Activity of Fe-S Cluster Requiring Proteins
United States Patent Application
The present invention is related to a recombinant host cell, in particular a yeast cell, comprising a dihydroxy-acid dehydratase polypeptide. The invention is also related to a recombinant host cell having increased specific activity of the dihydroxy-acid dehydratase polypeptide as a result of increased expression of the polypeptide, modulation of the Fe—S cluster biosynthesis of the cell, or a combination thereof. The present invention also includes methods of using the host cells, as well as, methods for identifying polypeptides that increase the flux in an Fe—S cluster biosynthesis pathway in a host cell.
Inventors:
Flint, Dennis (Newark, DE, US)
Paul, Brian James (Wilmington, DE, US)
Ye, Rick W. (Hockessin, DE, US)
Application Number:
Publication Date:
02/06/2014
Filing Date:
03/15/2013
Export Citation:
BUTAMAX(TM) ADVANCED BIOFUELS LLC (Wilmington, DE, US)
Primary Class:
Other Classes:
435/254.2,
435/254.22,
435/254.23
International Classes:
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Related US Applications:
January, 2010Deshayes et al.November, 2008Mechali et al.January, 2003Turnbull et al.August, 2008MarentisJanuary, 2010Nelson et al.April, 2009Dondi et al.September, 2005Lu et al.March, 2009Nagarajan et al.January, 2010Jensen et al.December, 2009Criddle et al.September, 2003Chang et al.
Foreign References:
Other References:
Guo et al., Protein tolerance to random amino acid change, 2004, Proc. Natl. Acad. Sci. USA 101: .
Lazar et al., Transforming Growth Factor alpha: Mutation of Aspartic Acid 47 and Leucine 48 Results in Different Biological Activity, 1988, Mol. Cell. Biol. 8:.
Hill et al., Functional Analysis of conserved Histidines in ADP-Glucose Pyrophosphorylase from Escherichia coli, 1998, Biochem. Biophys. Res. Comm. 244:573-577.
Wacey et al., Disentangling the perturbational effects of amino acid substitutions in the DNA-binding domain of p53., Hum Genet, 1999, Volume 104, pages 15-22.
Branden and Tooze, Introduction to Protein Structure (1999), 2nd edition, Garland Science Publisher, pages 3-12.
1. 1-62. (canceled)
A recombinant host cell comprising (i) at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase (DHAD) activity, and (ii) at least one deletion, mutation or substitution in an endogenous gene encoding FRA2, wherein the polypeptide having DHAD activity has an amino acid sequence that matches the Profile HMM of Table 12 with an E value of &10-5, and wherein the polypeptide farther comprises all three conserved cysteines, corresponding to positions 56, 129 and 201 in the amino acid sequences of the Streptococcus mutans DHAD enzyme corresponding to SEQ ID NO:168.
The recombinant host cell of claim 63, wherein the at least one heterologous polynucleotide encoding a polypeptide having DHAD activity is expressed in the cytosol of the recombinant host cell.
The recombinant host cell of claim 63, wherein the at least one deletion, mutation or substitution is in an endogenous gene encoding a polypeptide with at least about 90% identity to SEQ ID NO: 706.
The recombinant host cell of claim 63, wherein the at least one heterologous polynucleotide encoding a polypeptide having DHAD activity is expressed in multiple copies.
The recombinant host cell of claim 63, wherein the at least one heterologous polynucleotide encoding a polypeptide having DHAD activity is integrated at least once in the recombinant host cell DNA.
The recombinant host cell of claim 63, wherein the DHAD is a [2Fe-2S] DHAD.
The recombinant host cell of claim 63, wherein the recombinant host cell is a yeast host cell.
The recombinant host cell of claim 70, wherein the yeast host cell is Saccharomyces, Schizosaccharomyces, Hansenula, Candida, Kluyveromyces, Yarrowia, Issatchenkia, or Pichia.
The recombinant host cell of claim 70, wherein the yeast host cell is Saccharomyces cerevisiae.
The recombinant host cell of claim 63, wherein the recombinant host cell produces a branched chain amino acid, pantothenic acid, 2-methyl-1-butanol, 3-methyl-1-butanol, isobutanol, or combinations thereof.
The recombinant host cell of claim 63, wherein the recombinant host cell produces isobutanol.
The recombinant host cell of claim 63, wherein the recombinant host cell comprises an isobutanol biosynthetic pathway.
Description:
CROSS-REFERENCE TO RELATED APPLICATIONSThis application claims the benefit of U.S. Provisional Appl. No. 61/305,333, filed Feb. 17, 2010, which is incorporated by reference in its entirety.SEQUENCE LISTING INFORMATIONThe content of the electronically submitted sequence listing in ASCII text file CL4842sequencelisting.txt filed with the application is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION1. Field of the InventionThis invention relates generally to the fields of microbiology and biochemistry. Specifically, the present invention is related to a recombinant host cell, in particular a yeast cell, comprising a dihydroxy-acid dehydratase polypeptide. The invention is also related to a recombinant host cell having increased specific activity of the dihydroxy-acid dehydratase polypeptide as a result of increased expression of the polypeptide, modulation of the Fe—S cluster biosynthesis activity of the cell, or a combination thereof. The present invention also includes methods of using the host cells, as well as methods for identifying polypeptides that increase the flux in an Fe—S cluster biosynthesis pathway in a host cell.2. Background of the InventionIron-sulfur (Fe—S) clusters serve as cofactors or prosthetic groups essential for the normal function of the class of proteins that contain them. In the class of Fe—S cluster containing proteins, the Fe—S clusters have been found to play several roles. When proteins of this class are first synthesized by the cell, they lack the Fe—S clusters required for their proper function and are referred to as apoproteins. Fe—S clusters are made in a series of reactions by proteins involved in Fe—S cluster biosynthesis and are transferred to the apo-proteins to form the functional Fe—S cluster containing holoproteins.One such protein that requires Fe—S clusters for proper function is dihydroxy-acid dehydratase (DHAD) (E.C. 4.2.1.9). DHAD catalyzes the conversion of 2,3-dihydroxyisovalerate to α-ketoisovalerate, and of 2,3-dihydroxymethylvalerate to α-ketomethylvalerate. The DHAD enzyme is part of naturally occurring biosynthetic pathways producing the branched chain amino acids, (i.e., valine, isoleucine, leucine), and pantothenic acid (vitamin B5). DHAD catalyzed conversion of 2,3-dihydroxyisovalerate to α-ketoisovalerate is also a common step in the multiple isobutanol biosynthetic pathways that are disclosed in U.S. Patent Appl. Pub. No. US
A1, incorporated by reference herein. Disclosed therein is, e.g., the engineering of recombinant microorganisms for the production of isobutanol.High levels of DHAD activity are desired for increased production of products from biosynthetic pathways that include this enzyme activity, including, e.g., enhanced microbial production of branched chain amino acids, pantothenic acid, and isobutanol. Isobutanol, in particular, is useful as a fuel additive, and its ready availability may reduce the demand for petrochemical fuels. However, since all known DHAD enzymes require a Fe—S cluster for their function, they must be expressed in a host having the genetic machinery to provide the Fe—S clusters required by these proteins. In yeast, mitochondria play an essential role in Fe—S cluster biosynthesis. If the DHAD is to be functionally expressed in yeast cytosol, a system to transport the requisite Fe—S precursor or signal from mitochondria and assemble the Fe—S cluster on the cytosolic apoprotein is required. Prior to the work of the present inventors, it was previously unknown whether yeast could provide Fe—S clusters for any DHAD located in the cytoplasm (since native yeast DHAD is located in the mitochondria) and more importantly when the DHAD is expressed at high levels in the cytoplasmUnder certain conditions the rate of synthesis of Fe—S cluster requiring apo-proteins may exceed the cell's ability to synthesize and assemble Fe—S clusters for them. Cluster-less apo-proteins that accumulate under these conditions cannot carry out their normal function. Such conditions can include 1) the expression of a heterologous Fe—S cluster requiring protein especially in high amounts, 2) the expression of a native Fe—S cluster biosynthesis protein at higher levels than normal, or 3) a state where the host cell's ability to synthesize Fe—S clusters is debilitated.BRIEF SUMMARY OF THE INVENTIONDisclosed herein is the surprising discovery that recombinant host cells expressing a high level of a heterologous Fe—S cluster requiring protein can supply the complement of Fe—S clusters for that protein if the level(s) of at least one Fe uptake, utilization, and/or Fe—S cluster biosynthesis protein are altered.Provided herein are recombinant host cells comprising at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity wherein said at least one heterologous polynucleotide comprises a high copy number plasmid or a plasmid with a copy number that can be regulated. Also provided are recombinant host cells comprising at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity wherein said at least one heterologous polynucleotide is integrated at least once in the recombinant host cell DNA. Also provided are recombinant host cells comprising at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity, wherein said host cell comprises at least one deletion, mutation, and/or substitution in an endogenous gene encoding a polypeptide affecting iron metabolism or Fe—S cluster biosynthesis. Also provided are recombinant host cells comprising at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity and at least one heterologous polynucleotide encoding a polypeptide affecting iron metabolism or Fe—S cluster biosynthesis.In embodiments, said heterologous polynucleotide encoding a polypeptide affecting Fe—S cluster biosynthesis is selected from the group consisting of the genes in Tables 7, 8 and 9. In embodiments, said heterologous polynucleotide encoding a polypeptide affecting Fe—S cluster biosynthesis is selected from the group consisting of AFT1, AFT2, CCC1, FRA2, and GRX3, and combinations thereof. In embodiments, polypeptide is encoded by a polynucleotide that is constitutive mutant. In embodiments, said constitutive mutant is selected from the group consisting of AFT1 L99A, AFT1 L102A, AFT1 C291F, AFT1 C293F, and combinations thereof. In embodiments said polypeptide affecting Fe—S cluster biosynthesis is encoded by a polynucleotide comprising a high copy number plasmid or a plasmid with a copy number that can be regulated. In embodiments, said polypeptide affecting Fe—S cluster biosynthesis is encoded by a polynucleotide integrated at least once in the recombinant host cell DNA. In embodiments, the at least one deletion, mutation, and/or substitution in an endogenous gene encoding a polypeptide affecting Fe—S cluster biosynthesis is selected from the group consisting of CCC1, FRA2, and GRX3, and combinations thereof. In embodiments, the at least one heterologous polynucleotide encoding a polypeptide affecting Fe—S cluster biosynthesis is selected from the group consisting of AFT1, AFT2, their mutants, and combinations thereof.In embodiments, said at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity is expressed in multiple copies. In embodiments, said at least one heterologous polynucleotide comprises a high copy number plasmid or a plasmid with a copy number that can be regulated. In embodiments, said at least one heterologous polynucleotide is integrated at least once in the recombinant host cell DNA. In embodiments, said Fe—S cluster biosynthesis is increased compared to a recombinant host cell having endogenous Fe—S cluster biosynthesis.In embodiments, said host cell is a yeast host cell. In embodiments, said yeast host cell is selected from the group consisting of Saccharomyces, Schizosaccharomyces, Hansenula, Candida, Kluyveromyces, Yarrowia, Issatchenkia and Pichia. In embodiments, said heterologous polypeptide having dihydroxy-acid dehydratase activity is expressed in the cytosol of the host cell. In embodiments, said heterologous polypeptide having dihydroxy-acid dehydratase activity has an amino acid sequence that matches the Profile HMM of Table 12 with an E value of &10-5 wherein the polypeptide further comprises all three conserved cysteines, corresponding to positions 56, 129, and 201 in the amino acids sequences of the Streptococcus mutans DHAD enzyme corresponding to SEQ ID NO:168. In embodiments, said heterologous polypeptide having dihydroxy-acid dehydratase activity has an amino acid sequence with at least about 90% identity to SEQ ID NO: 168 or SEQ ID NO: 232. In embodiments said polypeptide having dihydroxy-acid dehydratase activity has a specific activity selected from the group consisting of: greater than about 5-fold with respect to the control host cell comprising at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity, greater than about 8-fold with respect to the control host cell comprising at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity, or greater than about 10-fold with respect to the control host cell comprising at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity. In embodiments said polypeptide having dihydroxy-acid dehydratase activity has a specific activity selected from the group consisting of: greater than about 3-fold with respect to a control host cell comprising at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity and greater than about 6-fold with respect to the control host cell comprising at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity. In embodiments, said polypeptide having dihydroxy-acid dehydratase activity has a specific activity selected from the group consisting of: greater than about 0.25 U/ greater than about 0.3 U/ greater than about 0.5 U/ greater than about 1.0 U/ greater than about 1.5 U/ greater than about 2.0 U/ greater than about 3.0 U/ greater than about 4.0 U/ greater than about 5.0 U/ greater than about 6.0 U/ greater than about 7.0 U/ greater than about 8.0 U/ greater than about 9.0 U/ greater than about 10.0 U/ greater than about 20.0 U/ and greater than about 50.0 U/mg.In embodiments said recombinant host cell produces isobutanol, and in embodiments, said recombinant host cell comprises an isobutanol biosynthetic pathway.Also provided herein are methods of making a product comprising: providing a r and contacting the recombinant host cell of with a fermentable carbon substrate in a fermentation medium under conditions wherein said wherein the product is selected from the group consisting of branched chain amino acids, pantothenic acid, 2-methyl-1-butanol, 3-methyl-1-butanol, isobutanol, and combinations thereof. In embodiments, the methods further comprise optionally recovering said product. In embodiments, the methods further comprise recovering said product.Also provided are methods of making isobutanol comprising: providing a r contacting the recombinant host cell with a fermentable carbon substrate in a fermentation medium under conditions wherein isobutanol is produced. In embodiments, the methods further comprise optionally recovering said isobutanol. In embodiments, the methods further comprise recovering said isobutanol.Also provided are methods for the conversion of 2,3-dihydroxyisovalerate to α-ketoisovalerate comprising: providing a r growing the recombinant host cell of under conditions where the 2,3-dihydroxyisovalerate is converted to α-ketoisovalerate. In embodiments, the conversion of 2,3-dihydroxyisovalerate to α-ketoisovalerate compared to a control host cell comprising at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity is increased in an amount selected from the group consisting of: (a) at least about 5%; (b) at least about 10%; (c) at least about 15%; (d) at least about 20%; (e) at least about 25%; (f) at least about 30%; (g) at least about 35%; (h) at least about 40%; (i) at least about 45%; (0 at least about 50%; (k) at least about 60%; (l) at least about 70%; (m) at least about 80%; (n) at least about 90%; and (o) at least about 95%.Also provided are methods for increasing the specific activity of a heterologous polypeptide having dihydroxy-acid dehydratase activity in a recombinant host cell comprising: providing a r and growing the recombinant host cell of under conditions whereby the heterologous polypeptide having dihydroxy-acid dehydratase activity is expressed in functional form having a specific activity greater than the same host cell lacking said heterologous polypeptide.Also provided are methods for increasing the flux in an Fe—S cluster biosynthesis pathway in a host cell comprising: providing a r and growing the recombinant host cell under conditions whereby the flux in the Fe—S cluster biosynthesis pathway in the host cell is increased.Also provide are methods of increasing the activity of an Fe—S cluster requiring protein in a recombinant host cell comprising: providing a recombinant host cell comprising an Fe—S clust changing the expression or activity of a polypeptide affecting Fe—S cluster biosynthes and growing the recombinant host cell under conditions whereby the activity of the Fe—S cluster requiring protein is increased, in embodiments, said increase in activity is an amount selected from the group consisting of: greater than about 10%; greater than about 20%; greater than about 30%; greater than about 40%; greater than about 50%; greater than about 60%; greater than about 70%; greater than about 80%; greater than about 90%; and greater than about 95%, 98%, or 99%. In embodiments, the increase in activity is in an amount selected from the group consisting of: greater than about 5- greater than about 8- greater than about 10-fold. In embodiments, the increase in activity is in an amount selected from the group consisting greater than about 3-fold and greater than about 6-fold.A method for identifying polypeptides that increase the flux in an Fe—S cluster biosynthesis pathway in a host cell comprising: changing the expression or activity of a polypeptide affecting Fe—S
measuring the activity of a heterologous Fe—S clust and comparing the activity of the heterologous Fe—S cluster requiring protein measured in the presence of the change in expression or activity of a polypeptide to the activity of the heterologous Fe—S cluster requiring protein measured in the absence of the change in expression or activity of a polypeptide, wherein an increase in the activity of the heterologous Fe—S cluster requiring protein indicates an increase in the flux in said Fe—S cluster biosynthesis pathway.Provided herein are methods for identifying polypeptides that increase the flux in an Fe—S cluster biosynthesis pathway in a host cell comprising: changing the expression or activity of a polypeptide affecting Fe—S
measuring the activity of a polypeptide having dihydroxy-acid
and comparing the activity of the polypeptide having dihydroxy-acid dehydratase activity measured in the presence of the change to the activity of the polypeptide having dihydroxy-acid dehydratase activity measured in the absence of change, wherein an increase in the activity of the polypeptide having dihydroxy-acid dehydratase activity indicates an increase in the flux in said Fe—S cluster biosynthesis pathway.In embodiments, said changing the expression or activity of a polypeptide affecting Fe—S cluster biosynthesis comprises deleting, mutating, substituting, expressing, up-regulating, down-regulating, altering the cellular location, altering the state of the protein, and/or adding a cofactor. In embodiments, the Fe—S cluster requiring protein has dihydroxy-acid dehydratase activity and wherein said Fe—S cluster requiring protein having dihydroxy-acid dehydratase activity has an amino acid sequence that matches the Profile HMM of Table 12 with an F value of &10-5 wherein the polypeptide further comprises all three conserved cysteines, corresponding to positions 56, 129, and 201 in the amino acids sequences of the Streptococcus mutans DHAD enzyme corresponding to SEQ ID NO:168, in embodiments, the polypeptide affecting Fe—S cluster biosynthesis is selected from the group consisting of the genes in Tables 7, 8 and 9.Also provided are recombinant host cells comprising at least one polynucleotide encoding a polypeptide identified by the methods provided herein. In embodiments, said host cell further comprises at least one heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity. In embodiments, said heterologous polynucleotide encoding a polypeptide having dihydroxy-acid dehydratase activity is expressed in multiple copies. In embodiments, said heterologous polynucleotide comprises a high copy number plasmid or a plasmid with a copy number that can be regulated. In embodiments, said heterologous polynucleotide is integrated at least once in the recombinant host cell DNA.In embodiments, said host cell is a yeast host cell. In embodiments, said yeast host cell is selected from the group consisting of Saccharomyces, Schizosaccharomyces, Hansenula, Candida, Kluyveromyces, Yarrowia, Issatchenkia, and Pichia. In embodiments, said heterologous polypeptide having dihydroxy-acid dehydratase activity is expressed in the cytosol of the host cell. In embodiments, said heterologous polypeptide having dihydroxy-acid dehydratase activity has an amino acid sequence that matches the Profile HMM of Table 12 with an E value of &10-5 wherein the polypeptide further comprises all three conserved cysteines, corresponding to positions 56, 129, and 201 in the amino acids sequences of the Streptococcus mutans MAD enzyme corresponding to SEQ NO:168. In embodiments, said recombinant host cell produces a product selected from the group consisting of branched chain amino acids, pantothenic acid, 2-methyl-1-butanol, 3-methyl-1-butanol, isobutanol, and combinations thereof. In embodiments, recombinant host cell produces isobutanol. In embodiments, said recombinant host cell comprises an isobutanol biosynthetic pathway. In embodiments said isobutanol biosynthetic pathway comprises at least one polypeptide encoded by a polynucleotide heterologous to the host cell. In embodiments, said isobutanol biosynthetic pathway comprises at least two polypeptides encoded by polynucleotides heterologous to the host cell.In embodiments, monomers of the polypeptides of the invention having dihydroxy-acid dehydratase activity have an Fe—S cluster loading selected from the group consisting of: (a) at least about 10%; (b) at least about 15%; (c) at least about 20%; (d) at least about 25%; (e) at least about 30%; (f) at least about 35%; (g) at least about 40%; (h) at least about 45%, (i) at least about 50%; (j) at least about 60%, (k) at least about 70%; (l) at least about 80%; (m) at least about 90% and (n) at least about 95%.BRIEF DESCRIPTION OF THE DRAWINGS/FIGURESFIG. 1A depicts a vector map of a vector for overexpression of the IlvD gene from S. mutans. FIG. 1B depicts a vector map of an integration vector for overexpression of the IlvD gene from S. mutans in the chromosome.FIG. 2 depicts a vector map of a centromere vector used to clone AFT1 or AFT1 mutants and useful for other genes of interest.FIG. 3 depicts a UV-Vis absorbance spectrum of purified S. mutans DHAD.FIG. 4 depicts an EPR spectrum of purified S. mutans DHAD. FIG. 5 depicts a biosynthetic pathway for biosynthesis of isobutanol.FIG. 6A depicts a schematic of Azotobacter vinelandlii nif genes.FIG. 6B depicts a schematic of additional Azotobacter vinelandii nif genes.FIG. 6C depicts a schematic of the equation in which NFU acts as a persuifide reductase.FIG. 7 depicts a schematic of Helicobacter pylori nif genes.FIG. 8 depicts a schematic of E. coli isc genes.FIG. 9 depicts a schematic of E. coli suf genes.FIG. 10 depicts a schematic of the cytosolic [2Fe-2S] biosynthesis and assembly system.FIG. 11 depicts a vector map of a vector for overexpression of the IlvD gene from L. lactis. Table 12 is a table of the Profile HMM for dihydroxy-acid dehydratases based on enzymes with assayed function prepared as described in U.S. patent application Ser. No. 12/569,636, filed Sep. 29, 2009. Table 12 is submitted herewith electronically and is incorporated herein by reference.DETAILED DESCRIPTION OF THE INVENTIONDescribed herein is a method to increase the fraction of the Fe—S cluster requiring proteins that are loaded with Fe—S clusters. Also described are recombinant host cells that express functional Fe—S cluster requiring proteins, such as DHAD enzymes, and at least one heterologous Fe uptake, utilization, or Fe—S cluster biosynthesis protein, recombinant host cells that express functional DHAD enzymes and comprise at least one deletion, mutation, and/or substitution in a native protein involved in Fe utilization or Fe—S cluster biosynthesis, or recombinant host cells comprising combinations thereof. In addition, the present invention describes a method to identify polypeptides that increase the flux in an Fe—S cluster biosynthesis pathway in a host cell. Also described is a method to identify polypeptides that alter the activity of an Fe—S cluster requiring protein.DEFINITIONSUnless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present application including the definitions will control. Also, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. All publications, patents and other references mentioned herein are incorporated by reference in their entireties for all purposes.In order to further define this invention, the following terms and definitions are herein provided.As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains” or “containing,” or any other variation thereof, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. For example, a composition, a mixture, a process, a method, an article, or an apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).As used herein, the term “consists of,” or variations such as “consist of” or “consisting of” as used throughout the specification and claims, indicate the inclusion of any recited integer or group of integers, but that no additional integer or group of integers may be added to the specified method, structure, or composition.As used herein, the term “consists essentially of,” or variations such as “consist essentially of” or “consisting essentially of,” as used throughout the specification and claims, indicate the inclusion of any recited integer or group of integers, and the optional inclusion of any recited integer or group of integers that do not materially change the basic or novel properties of the specified method, structure or composition. See M.P.E.P. §2111.03.Also, the indefinite articles “a” and “an” preceding an element or component of the invention are intended to be nonrestrictive regarding the number of instances, i.e., occurrences of the element or component. Therefore “a” or “an” should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.The term “invention” or “present invention” as used herein is a non-limiting term and is not intended to refer to any single embodiment of the particular invention but encompasses all possible embodiments as described in the application.As used herein, the term “about” modifying the quantity of an ingredient or reactant of the invention employed refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or solutio through inadvertent error through differences in the manufacture, source, or purity of the ingredients employed to make the compositions or to c and the like. The term “about” also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term “about”, the claims include equivalents to the quantities. In one embodiment, the term “about” means within 10% of the reported numerical value, preferably within 5% of the reported numerical value.The term “isobutanol biosynthetic pathway” refers to an enzyme pathway to produce isobutanol from pyruvate.The term “a facultative anaerobe” refers to a microorganism that can grow in both aerobic and anaerobic environments.The term “carbon substrate” or “fermentable carbon substrate” refers to a carbon source capable of being metabolized by host organisms of the present invention and particularly carbon sources selected from the group consisting of monosaccharides, oligosaccharides, polysaccharides, and one-carbon substrates or mixtures thereof.The term “Fe—S cluster biosynthesis” refers to biosynthesis of Fe—S clusters, including, e.g., the assembly and loading of Fe—S clusters. The term “Fe—S cluster biosynthesis genes”, “Fe—S cluster biosynthesis proteins” or “Fe—S cluster biosynthesis pathway” refers to those polynucleotides/genes and the encoded polypeptides that are involved in the biosynthesis of Fe—S clusters, including, e.g., the assembly and loading of Fe—S clusters.The term “Fe uptake and utilization” refers to processes which can effect Fe—S cluster biosynthesis such as Fe sensing, uptake, utilization, and homeostasis. “Fe uptake and utilization genes” refers to those polynucleotides/genes and the encoded polypeptides that are involved in Fe uptake, utilization, and homeostasis. Some of these polynucleotides/genes are contained in the “Fe Regulon” that has been described in the literature and is further described hereafter. As used herein, Fe uptake and utilization genes and Fe—S cluster biosynthesis genes can encode a polypeptide affecting Fe—S cluster biosynthesis.The term “specific activity” as used herein is defined as the units of activity in a given amount of protein. Thus, the specific activity is not directly measured but is calculated by dividing 1) the activity in units/ml of the enzyme sample by 2) the concentration of protein in that sample, so the specific activity is expressed as units/mg. The specific activity of a sample of pure, fully active enzyme is a characteristic of that enzyme. The specific activity of a sample of a mixture of proteins is a measure of the relative fraction of protein in that sample that is composed of the active enzyme of interest. The specific activity of a polypeptide of the invention may be selected from greater than about 0.25 U/ greater than about 0.3 U/ greater than about 0.4 U/ greater than about 0.5 U/ greater than about 0.6 U/ greater than about 0.7 U/ greater than about 0.8 U/ greater than about 0.9 U/ greater than about 1.0 U/ greater than about 1.5 U/ greater than about 2.0 U/ greater than about 2.5 U/ greater than about 3.0 U/ greater than about 15 U/ greater than about 4.0 U/ greater than about 5.5 U/ greater than about 5.0 U/ greater than about 6.0 U/ greater than about 6.5 U/ greater than about 7.0 U/ greater than about 7.5 U/ greater than about 8.0 U/ greater than about 8.5 U/ greater than about 9.0 U/ greater than about 9.5 U/ greater than about 10.0 U/ greater than about 20.0 U/ or greater than about 50.0 U/mg. In one embodiment, the specific activity of a polypeptide of the invention is greater than about 0.25 U/mg. I the specific activity is greater than about 1.0 U/mg. In yet another embodiment, the specific activity is greater than about 2.0 U/mg or greater than about 3.0 U/mg.The term “polynucleotide” is intended to encompass a singular nucleic acid as well as plural nucleic acids, and refers to a nucleic acid molecule or construct, e.g., messeger RNA (mRNA) or plasmid DNA (pDNA). A polynucleotide can contain the nucleotide sequence of the full-length cDNA sequence, or a fragment thereof, including the untranslated 5 and 3′ sequences and the coding sequences. The polynucleotide can be composed of any polyribonucleotide or polydeoxyribonucleotide, which may be unmodified RNA or DNA or modified RNA or DNA. For example, polynucleotides can be composed of single- and double-stranded DNA, DNA that is a mixture of single- and double-stranded regions, single- and double-stranded RNA, and RNA that is mixture of single- and double-stranded regions, hybrid molecules comprising DNA and RNA that may be single-stranded or, more typically, double-stranded or a mixture of single- and double-stranded regions. “Polynucleotide” embraces chemically, enzymatically, or metabolically modified forms.A polynucleotide sequence may be referred to as “isolated,” in which it has been removed from its native environment. For example, a heterologous polynucleotide encoding a polypeptide or polypeptide fragment having dihydroxy-acid dehydratase activity contained in a vector is considered isolated for the purposes of the present invention. Further examples of an isolated polynucleotide include recombinant polynucleotides maintained in heterologous host cells or purified (partially or substantially) polynucleotides in solution. Isolated polynucleotides or nucleic acids according to the present invention further include such molecules produced synthetically. An isolated polynucleotide fragment in the form of a polymer of DNA may be comprised of one or more segments of cDNA, genomic DNA or synthetic DNA.The term “gene” refers to a polynucleotide that is capable of being expressed as a specific protein, optionally including regulatory sequences preceding (5′ non-coding sequences) and following (3° non-coding sequences) the coding sequence. “Native gene” refers to a gene as found in nature with its own regulatory sequences. “Chimeric gene” refers to any gene that is not a native gene, comprising regulatory and coding sequences that are not found together in nature. Accordingly, a chimeric gene may comprise regulatory sequences and coding sequences that are derived from different sources, or regulatory sequences and coding sequences derived from the same source, but arranged in a manner different than that found in nature.As used herein, a “coding region” is a portion of nucleic acid which consists of codons translated into amino acids. Although a “stop codon” (TAG, TGA, or TAA) is not translated into an amino acid, it may be considered to be part of a coding region, but any flanking sequences, for example promoters, ribosome binding sites, transcriptional terminators, introns, and the like, are not part of a coding region. Two or more coding regions of the present invention can be present in a single polynucleotide construct, e.g., on a single vector, or in separate polynucleotide constructs, e.g., on separate (different) vectors. Furthermore, any vector may contain a single coding region, or may comprise two or more coding regions. In addition, a vector, polynucleotide, or nucleic acid of the invention may encode heterologous coding regions.The term “endogenous,” when used in reference to a polynucleotide, a gene, or a polypeptide refers to a native polynucleotide or gene in its natural location in the genome of an organism, or for a native polypeptide, is transcribed and translated from this location in the genome.The term “heterologous” when used in reference to a polynucleotide, a gene, or a polypeptide refers to a polynucleotide, gene, or polypeptide not normally found in the host organism. “Heterologous” also includes a native coding region, or portion thereof, that is reintroduced into the source organism in a form that is different from the corresponding native gene, e.g., not in its natural location in the organism's genome. The heterologous polynucleotide or gene may be introduced into the host organism by, e.g., gene transfer. A heterologous gene may include a native coding region with non-native regulatory regions that is reintroduced into the native host. A “transgene” is a gene that has been introduced into the genome by a transformation procedure.The term “recombinant genetic expression element” refers to a nucleic acid fragment that expresses one or more specific proteins, including regulatory sequences preceding (5′ non-coding sequences) and following (3′ termination sequences) coding sequences for the proteins. A chimeric gene is a recombinant genetic expression element. The coding regions of an operon may form a recombinant genetic expression element, along with an operably linked promoter and termination region.“Regulatory sequences” refers to nucleotide sequences located upstream (5′ non-coding sequences), within, or downstream (3′ non-coding sequences) of a coding sequence, and which influence the transcription, RNA processing or stability, or translation of the associated coding sequence. Regulatory sequences may include promoters, enhancers, operators, repressors, transcription termination signals, translation leader sequences, introns, polyadenylation recognition sequences, RNA processing site, effector binding site and stem-loop structure.The term “promoter” refers to a nucleic acid sequence capable of controlling the expression of a coding sequence or functional RNA. In general, a coding sequence is located 3′ to a promoter sequence. Promoters may be derived in their entirety from a native gene, or be composed of different elements derived from different promoters found in nature, or even comprise synthetic nucleic acid segments it is understood by those skilled in the art that different promoters may direct the expression of a gene in different tissues or cell types, or at different stages of development, or in response to different environmental or physiological conditions. Promoters which cause a gene to be expressed in most cell types at most times are commonly referred to as “constitutive promoters”. “inducible promoters,” on the other hand, cause a gene to be expressed when the promoter is induced or turned on by a promoter-specific signal or molecule. It is further recognized that since in most cases the exact boundaries of regulatory sequences have not been completely defined, DNA fragments of different lengths may have identical promoter activity.The term “operably linked” refers to the association of nucleic acid sequences on a single nucleic acid fragment so that the function of one is affected by the other. For example, a promoter is operably linked with a coding sequence when it is capable of effecting the expression of that coding sequence (i.e., that the coding sequence is under the transcriptional control of the promoter). Coding sequences can be operably linked to regulatory sequences in sense or antisense orientation.The term “expression”, as used herein, refers to the transcription and accumulation of sense (mRNA) or antisense RNA derived from the nucleic acid fragment of the invention. Expression may also refer to translation of mRNA into a polypeptide. The process includes any manifestation of the functional presence of the expressed polynucleotide, gene, or polypeptide within the cell including, without limitation, gene knockdown as well as both transient expression and stable expression.The term “over-expression”, as used herein, refers to expression that is higher than endogenous expression of the same or related polynucleotide or gene. A heterologous polynucleotide or gene is also over-expressed if its expression is higher than that of a comparable endogenous gene, or if its expression is higher than that of the same polynucleotide or gene introduced by a means that does not overexpress the polynucleotide or gene. For example, a polynucleotide can be expressed in a host cell from a low copy number plasmid, which is present in only limited or few copies, and the same polynucleotide can be over-expressed in a host cell from a high copy number plasmid or a plasmid with a copy number that can be regulated, which is present in multiple copies. Any means can be used to over-express a polynucleotide, so long as it increases the copies of the polynucleotide in the host cell. In addition to using a high copy number plasmid, or a plasmid with a copy number that can be regulated, a polynucleotide can be over-expressed by multiple chromosomal integrations.Expression or over-expression of a polypeptide of the invention in a recombinant host cell can be quantified according to any number of methods known to the skilled artisan and can be represented, e.g., by a percent of total cell protein. The percent of total protein can be an amount selected from greater than about 0.001% o greater than about 0.01% o greater than about 0.1% o greater than about 0.5% o greater than about 1.0% o greater than about 2.0% o greater than about 3% o greater than about 4.0% o greater than about 5% o greater than about 6.0% o greater than about 7.0% o greater than about 8.0% o greater than about 9.0% o greater than about 10% o or greater than about 20% of total cell protein. In one embodiment, the amount of polypeptide expressed is greater that about 0.5% of total cell protein. In another embodiment, the amount of polypeptide expressed is greater than about 1.0% of total cell protein or greater than about 2.0% of total cell protein.As used herein the term “transformation” refers to the transfer of a nucleic acid fragment into a host organism, resulting in genetically stable inheritance with or without selections. Host organisms containing the transformed nucleic acid fragments are referred to as “transgenic” or “recombinant” or “transformed” organisms.The terms “plasmid” and “vector” as used herein, refer to an extra chromosomal element often carrying genes which are not part of the central metabolism of the cell, and usually in the form of circular double-stranded DNA molecules. Such elements may be autonomously replicating sequences, genome integrating sequences, phage or nucleotide sequences, linear or circular, of a single- or double-stranded DNA or RNA, derived from any source, in which a number of nucleotide sequences have been joined or recombined into a unique construction which is capable of introducing a promoter fragment and DNA sequence for a selected gene product along with appropriate 3′ untranslated sequence into a cell.As used herein the term “codon degeneracy” refers to the nature in the genetic code permitting variation of the nucleotide sequence without effecting the amino acid sequence of an encoded polypeptide. The skilled artisan is well aware of the “codon-bias” exhibited by a specific host cell in usage of nucleotide codons to specify a given amino acid. Therefore, when synthesizing a gene for improved expression in a host cell, it is desirable to design the gene such that its frequency of codon usage approaches the frequency of preferred codon usage of the host cell.The term “codon-optimized” as it refers to genes or coding regions of nucleic acid molecules for transformation of various hosts, refers to the alteration of codons in the gene or coding regions of the nucleic acid molecules to reflect the typical codon usage of the host organism without altering the polypeptide encoded by the DNA. Such optimization includes replacing at least one, or more than one, or a significant number, of codons with one or more codons that are more frequently used in the genes of that organism.Deviations in the nucleotide sequence that comprise the codons encoding the amino acids of any polypeptide chain allow for variations in the sequence coding for the gene. Since each codon consists of three nucleotides, and the nucleotides comprising DNA are restricted to four specific bases, there are 64 possible combinations of nucleotides, 61 of which encode amino acids (the remaining three codons encode signals ending translation). The “genetic code” which shows which codons encode which amino acids is reproduced herein as Table 1. As a result, many amino acids are designated by more than one codon. For example, the amino acids alanine and proline are coded for by four triplets, serine and arginine by six, whereas tryptophan and methionine are coded by just one triplet. This degeneracy allows for DNA base composition to vary over a wide range without altering the amino acid sequence of the proteins encoded by the DNA.TABLE 1The Standard Genetic CodeTCAGTTTT Phe (F)TCT Ser (S)TAT Tyr TGT Cys (Y)(C) TTC Phe (F)TCC Ser (S)TAC Tyr TGC(Y) TTA Leu (L)TCA Ser (S)TAA TGA StopStop TTG Leu (L)TCG Ser (S)TAG TGG Trp Stop(W) CCTT Leu (L)CCT Pro (P)CAT His CGT Arg (H)(R) CTC Leu (L)CCC Pro (P)CAC His CGC Arg (H)(R) CTA Leu (L)CCA Pro (P)CAA Gln CGA Arg (Q)(R) CTG Leu (L)CCG Pro (P)CAG Gln CGG Arg (Q)(R) AATT Ile (I)ACT Thr (T)AAT Asn AGT Ser (N)(S) ATC Ile (I)ACC Thr (T)AAC Asn AGC Ser (N)(S) ATA Ile (I)ACA Thr (T)AAA Lys AGA Arg (K)(R) ATG MetACG Thr (T)AAG Lys AGG Arg (M)(K)(R) GGTT Val (V)GCT Ala (A)GAT Asp GGT Gly (D)(G) GTC Val (V)GCC Ala (A)GAC Asp GGC Gly (D)(G) GTA Val (V)GCA Ala (A)GAA Glu GGA Gly (E)(G) GTG Val (V)GCG Ala (A)GAG Glu GGG Gly (E)(G) Many organisms display a bias for use of particular codons to code for insertion of a particular amino acid in a growing peptide chain. Codon preference, or codon bias, differences in codon usage between organisms, is afforded by degeneracy of the genetic code, and is well documented among many organisms. Codon bias often correlates with the efficiency of translation of messenger RNA (mRNA), which is in turn believed to be dependent on, inter alia, the properties of the codons being translated and the availability of particular transfer RNA (tRNA) molecules. The predominance of selected tRNAs in a cell is generally a reflection of the codons used most frequently in peptide synthesis. Accordingly, genes can be tailored for optimal gene expression in a given organism based on codon optimization.Given the large number of gene sequences available for a wide variety of animal, plant and microbial species, it is possible to calculate the relative frequencies of codon usage. Codon usage tables are readily available, for example, at the “Codon Usage Database” available at http://www.kazusa.or.jp/codon/ (visited Mar. 20, 2008), and these tables can be adapted in a number of ways. See Nakamura, Y., et al. Nucl. Acids Res. 28:292 (2000). Codon usage tables for yeast, calculated from GenBank Release 128.0 [15 Feb. 2002], are reproduced below as Table 2. This table uses mRNA nomenclature, and so instead of thymine (T) which is found in DNA, the tables use uracil (U) which is found in RNA. Table 2 has been adapted so that frequencies are calculated for each amino acid, rather than for all 64 codons.TABLE 2Codon Usage Table for Saccharomycescerevisiae GenesFrequencyAminoperAcidCodonNumberthousandPheUUU17066626.1 PheUUC12051018.4 LeuUUA17088426.2 LeuUUG17757327.2 LeuCUU 8007612.3 LeuCUC 355455.4 LeuCUA 8761913.4 LeuCUG 6849410.5 IleAUU19689330.1 IleAUC11217617.2 IleAUA11625417.8 MetAUG13680570.9 ValGUU14424322.1 ValGUC 7694711.8 ValGUA 7692711.8 ValGUG 7033710.8 SerUCU15355723.5 SerUCC 9292314.2 SerUCA12202818.7 SerUCG 559518.6 SerAGU 9246614.2 SerAGC 637269.8 ProCCU 8826313.5 ProCCC 443096.8 ProCCA11964118.3 ProCCG 345975.3 ThrACU13252220.3 ThrACC 8320712.7 ThrACA11608417.8 ThrACG 520458.0 AlaGCU13835821.2 AlaGCC 8235712.6 AlaGCA10591016.2 AlaGCG 403586.2 TyrUAU12272818.8 TyrUAC 9659614.8 HisCAU 8900713.6 HisCAC 507857.8 GlnCAA17825127.3 GlnCAG 7912112.1 AsnAAU23312435.7 AsnAAC16219924.8 LysAAA27361841.9 LysAAG20136130.8 AspGAU24564137.6 AspGAC13204820.2 GluGAA29794445.6 GluGAG12571719.2 CysUGU 529038.1 CysUGC 310954.8 TrpUGG 6778910.4 ArgCGU 417916.4 ArgCGC 169932.6 ArgCGA 195623.0 ArgCGG 113511.7 ArgAGA13908121.3 ArgAGG 602899.2 GlyGGU15610923.9 GlyGGC 639039.8 GlyGGA 7121610.9 GlyGGG 393596.0 StopUAA 69131.1 StopUAG 33120.5 StopUGA 44470.7 By utilizing this or similar tables, one of ordinary skill in the art can apply the frequencies to any given polypeptide sequence, and produce a nucleic acid fragment of a codon-optimized coding region which encodes the polypeptide, but which uses codons optimal for a given species.Randomly assigning codons at an optimized frequency to encode a given polypeptide sequence, can be done manually by calculating codon frequencies for each amino acid, and then assigning the codons to the polypeptide sequence randomly. Additionally, various algorithms and computer software programs are readily available to those of ordinary skill in the art. For example, the “EditSeq” function in the Lasergene Package, available from DNAstar, Inc., Madison, Wis., the backtransiation function in the Vector NTI Suite, available from InforMax, Inc., Bethesda, Md., and the “backtranslate” function in the GCG-Wisconsin Package, available from Accehys, Inc., San Diego, Calif. In addition, various resources are publicly available to codon-optimize coding region sequences, e.g., the “backtranslation” function at http://www.entelechon.com/bioinformatics/backtranslation.php?lang=eng (visited Apr. 15, 2008) and the “backtranseq” function available at http://bioinfo.pbi.nrc.ca:8090/EMBOSS/index.html (visited Jul. 9, 2002). Constructing a rudimentary algorithm to assign codons based on a given frequency can also easily be accomplished with basic mathematical functions by one of ordinary skill in the art.Codon-optimized coding regions can be designed by various methods known to those skilled in the art including software packages such as “synthetic gene designer” (http://phenotype.biosci.umbc.edu/codon/sgd/index.php).As used herein, the term “polypeptide” is intended to encompass a singular “polypeptide” as well as plural “polypeptides,” and refers to a molecule composed of monomers (amino acids) linearly linked by amide bonds (also known as peptide bonds). The term “polypeptide” refers to any chain or chains of two or more amino acids, and does not refer to a specific length of the product. Thus, peptides, dipeptides, tripeptides, oligopeptides, “protein,” “amino acid chain,” or any other term used to refer to a chain or chains of two or more amino acids, are included within the definition of “polypeptide,” and the term “polypeptide” may be used instead of, or interchangeably with any of these terms. A polypeptide may be derived from a natural biological source or produced by recombinant technology, but is not necessarily translated from a designated nucleic acid sequence. It may be generated in any manner, including by chemical synthesis.By an “isolated” polypeptide or a fragment, variant, or derivative thereof is intended a polypeptide that is not in its natural milieu. No particular level of purification is required. For example, an isolated polypeptide can be removed from its native or natural environment. Recombinantly produced polypeptides and proteins expressed in host cells are considered isolated for purposed of the invention, as are native or recombinant polypeptides which have been separated, fractionated, or partially or substantially purified by any suitable technique.As used herein, the term “variant” refers to a polypeptide differing from a specifically recited polypeptide of the invention, such as DHAD, by amino acid insertions, deletions, mutations, and substitutions, created using, e.g., recombinant DNA techniques, such as mutagenesis. Guidance in determining which amino acid residues may be replaced, added, or deleted without abolishing activities of interest, may be found by comparing the sequence of the particular polypeptide with that of homologous polypeptides, e.g., yeast or bacterial, and minimizing the number of amino acid sequence changes made in regions of high homology (conserved regions) or by replacing amino acids with consensus sequences.Alternatively, recombinant polynucleotide variants encoding these same or similar polypeptides may be synthesized or selected by making use of the “redundancy” in the genetic code. Various codon substitutions, such as silent changes which produce various restriction sites, may be introduced to optimize cloning into a plasmid or viral vector for expression. Mutations in the polynucleotide sequence may be reflected in the polypeptide or domains of other peptides added to the polypeptide to modify the properties of any part of the polypeptide. For example, mutations can be used to reduce or eliminate expression of a target protein and include, but are not limited to, deletion of the entire gene or a portion of the gene, inserting a DNA fragment into the gene (in either the promoter or coding region) so that the protein is not expressed or expressed at lower introducing a mutation into the coding region which adds a stop codon or frame shift such that a functional protein is not expressed, and introducing one or more mutations into the coding region to alter amino acids so that a non-functional or a less enzymatically active protein is expressed.Amino acid “substitutions” may be the result of replacing one amino acid with another amino acid having similar structural and/or chemical properties, i.e., conservative amino acid replacements, or they may be the result of replacing one amino acid with an amino acid having different structural and/or chemical properties, i.e., non-conservative amino acid replacements. “Conservative” amino acid substitutions may be made on the basis of similarity in polarity, charge, solubility, hydrophobicity, hydrophilicity, or the amphipathic nature of the residues involved. For example, nonpolar (hydrophobic) amino acids include alanine, leucine, isoleucine, valine, proline, phenylalanine, tryptophan, polar neutral amino acids include glycine, serine, threonine, cysteine, tyrosine, asparagine, positively charged (basic) amino acids include arginine, lysine, and negatively charged (acidic) amino acids include aspartic acid and glutamic acid. Alternatively, “non-conservative” amino acid substitutions may be made by selecting the differences in polarity, charge, solubility, hydrophobicity, hydrophilicity, or the amphipathic nature of any of these amino acids. “Insertions” or “deletions” may be within the range of variation as structurally or functionally tolerated by the recombinant proteins. The variation allowed may be experimentally determined by systematically making insertions, deletions, or substitutions of amino acids in a polypeptide molecule using recombinant DNA techniques and assaying the resulting recombinant variants for activity.A “substantial portion” of an amino acid or nucleotide sequence is that portion comprising enough of the amino acid sequence of a polypeptide or the nucleotide sequence of a gene to putatively identify that polypeptide or gene, either by manual evaluation of the sequence by one skilled in the art, or by computer-automated sequence comparison and identification using algorithms such as BLAST (Altschul, S. F., et al., J. Mol. Biol.,
(1993)). In general, a sequence of ten or more contiguous amino acids or thirty or more nucleotides is necessaty in order to putatively identify a polypeptide or nucleic acid sequence as homologous to a known protein or gene. Moreover, with respect to nucleotide sequences, gene specific oligonucleotide probes comprising 20-30 contiguous nucleotides may be used in sequence-dependent methods of gene identification (e.g., Southern hybridization) and isolation (e.g., in situ hybridization of bacterial colonies or bacteriophage plaques). In addition, short oligonucleotides of 12-15 bases may be used as amplification primers in PCR in order to obtain a particular nucleic acid fragment comprising the primers. Accordingly, a “substantial portion” of a nucleotide sequence comprises enough of the sequence to specifically identify and/or isolate a nucleic acid fragment comprising the sequence. The instant specification teaches the complete amino acid and nucleotide sequence encoding particular proteins. The skilled artisan, having the benefit of the sequences as reported herein, may now use all or a substantial portion of the disclosed sequences for purposes known to those skilled in this art. Accordingly, the instant invention comprises the complete sequences as reported in the accompanying Sequence Listing, as well as substantial portions of those sequences as defined above.The term “complementary” is used to describe the relationship between nucleotide bases that are capable of hybridizing to one another. For example, with respect to DNA, adenine is complementary to thymine and cytosine is complementary to guanine, and with respect to RNA, adenine is complementary to uracil and cytosine is complementary to guanineThe term “percent identity”, as known in the art, is a relationship between two or more polypeptide sequences or two or more polynucleotide sequences, as determined by comparing the sequences. In the art, “identity” also means the degree of sequence relatedness between polypeptide or polynucleotide sequences, as the case may be, as determined by the match between strings of such sequences. “Identity” and “similarity” can be readily calculated by known methods, including but not limited to those described in: 1.) Computational Molecular Biology (Lesk, A. M., Ed.) Oxford University: NY (1988); 2.) Biocomputing: Informatics and Genome Projects (Smith, D. W., Ed.) Academic: NY (1993); 3.) Computer Analysis of Sequence Data, Part I (Griffin, A. M., and Griffin, H. G., Eds.) Humania: NJ (1994); 4.) Sequence Analysis in Molecular Biology (von Heine, G., Ed.) Academic (1987); and 5.) Sequence Analysis Primer (Gribskov, M. and Devereux, J., Eds.) Stockton: NY (1991).Preferred methods to determine identity are designed to give the best match between the sequences tested. Methods to determine identity and similarity are codified in publicly available computer programs. Sequence alignments and percent identity calculations may be performed using the MegAlign(TM) program of the LASERGENE bioinformatics computing suite (DNASTAR Inc., Madison, Wis.). Multiple alignments of the sequences is performed using the “Clustal method of alignment” which encompasses several varieties of the algorithm including the “Clustal V method of alignment” corresponding to the alignment method labeled Clustal V (described by Higgins and Sharp, CABIOS. 5:151-153 (1989); Higgins, D. G. et al., Comput. Appl. Biosci., 8:189-191 (1992)) and found in the MegAlign(TM) program of the LASERGENE bioinformatics computing suite (DNASTAR Inc.). For multiple alignments, the default values correspond to GAP PENALTY=10 and GAP LENGTH PENALTY=10. Default parameters for pairwise alignments and calculation of percent identity of protein sequences using the Clustal method are KTUPLE=1, GAP PENALTY=3, WINDOW=5 and DIAGONALS SAVED=5. For nucleic acids these parameters are KTUPLE=2, GAP PENALTY=5, WINDOW=4 and DIAGONALS SAVED=4. After alignment of the sequences using the Clustal V program, it is possible to obtain a “percent identity” by viewing the “sequence distances” table in the same program. Additionally the “Clustal W method of alignment” is available and corresponds to the alignment method labeled Clustal W (described by Higgins and Sharp, CABIOS. 5:151-153 (1989); Higgins, D. G. et al., Comput. Appl. Biosci. 8:189-191(1992)) and found in the MegAlign(TM) v6.1 program of the LASERGENE bioinformatics computing suite (DNASTAR Inc.). Default parameters for multiple alignment (GAP PENALTY=10, GAP LENGTH PENALTY=0.2, Delay Divergen Seqs (%)=30, DNA Transition Weight=0.5, Protein Weight Matrix=Gonnet Series, DNA Weight Matrix=IUB). After alignment of the sequences using the Clustal W program, it is possible to obtain a “percent identity” by viewing the “sequence distances” table in the same program.It is well understood by one skilled in the art that many levels of sequence identity are useful in identifying polypeptides, from other species, wherein such polypeptides have the same or similar function or activity, or in describing the corresponding polynucleotides. Useful examples of percent identities include, but are not limited to: 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%, or any integer percentage from 55% to 100% may be useful in describing the present invention, such as 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%. Suitable polynucleotide fragments not only have the above homologies but typically comprise a polynucleotide having at least 50 nucleotides, at least 100 nucleotides, at least 150 nucleotides, at least 200 nucleotides, or at least 250 nucleotides. Further, suitable polynucleotide fragments having the above homologies encode a polypeptide having at least 50 amino acids, at least 100 amino acids, at least 150 amino acids, at least 200 amino acids, or at least 250 amino acids.The term “sequence analysis software” refers to any computer algorithm or software program that is useful for the analysis of nucleotide or amino acid sequences. “Sequence analysis software” may be commercially available or independently developed. Typical sequence analysis software will include, but is not limited to: 1.) the GCG suite of programs (Wisconsin Package Version 9.0, Genetics Computer Group (GCG), Madison, Wis.); 2.) BLASTP, BLASTN, BLASTX (Altschul et al., J. Mol. Biol., 215:403-410 (1990)); 3.) DNASTAR (DNASTAR, Inc. Madison, Wis.); 4.) SEQUENCHER (Gene Codes Corporation, Ann Arbor, Mich.); and 5.) the RASTA program incorporating the Smith-Waterman algorithm (W. R. Pearson, Comput. Methods Genome Res., [Prot. Int. Symp.] (1994), Meeting Date . Editor(s): Suhai, Sandor. Plenum: New York, N.Y.). Within the context of this application it will be understood that where sequence analysis software is used for analysis, that the results of the analysis will be based on the “default values” of the program referenced, unless otherwise specified. As used herein “default values” will mean any set of values or parameters that originally load with the software when first initialized.Standard recombinant DNA and molecular cloning techniques used herein are well known in the art and are described by Sambrook, J., Fritsch, E. F. and Maniatis, T., Molecular Cloning: A Laboratory Manual, Second Edition, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1989) (hereinafter “Maniatis”); and by Silhavy, T. J., Berman, M. L. and Enquist, L. W., Experiments with Gene Fusions, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1984); and by Ausubel, F, M. et al., Current Protocols in Molecular Biology, published by Greene Publishing Assoc. and Wiley-Interscience (1987).The Functions of Fe—S Cluster-Requiring ProteinsThe functions of proteins that contain Fe—S clusters are diverse. One of the more complete efforts to classify these functions is given in the following table which is adapted from Johnson. D. C., et al., Structure, function, and formation of biological iron sulfur clusters. Annu. Rev, Biochem., 2005. 74: p. 247-281.TABLE 3Functions of Biological [Fe—S] clustersa.FunctionExamplesCluster typeElectron transferF redox[2Fe—2S]; [3Fe—4S]; [4Fe—4S]enzymesCoupled electron/protonRieske protein[2Fe—2S]transferNitrogenase[8Fe—7S]Substrate binding and(de)Hydratases[4Fe—4S], [2Fe—2S]activationRadical SAM enzymes[4Fe—4S]Acetyl-CoA synthaseNi—Ni—[4Fe—4S], [Ni—4Fe—5S]Sulfite reductase[4Fe—4S]-sirohemeFe or cluster storageFerredoxins[4Fe—4S]Polyferredoxins[4Fe—4S]StructuralEndonuclease III[4Fe—4S]MutY[4Fe—4S]}