1
|
Stripp ST, Duffus BR, Fourmond V, Léger C, Leimkühler S, Hirota S, Hu Y, Jasniewski A, Ogata H, Ribbe MW. Second and Outer Coordination Sphere Effects in Nitrogenase, Hydrogenase, Formate Dehydrogenase, and CO Dehydrogenase. Chem Rev 2022; 122:11900-11973. [PMID: 35849738 PMCID: PMC9549741 DOI: 10.1021/acs.chemrev.1c00914] [Citation(s) in RCA: 55] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Gases like H2, N2, CO2, and CO are increasingly recognized as critical feedstock in "green" energy conversion and as sources of nitrogen and carbon for the agricultural and chemical sectors. However, the industrial transformation of N2, CO2, and CO and the production of H2 require significant energy input, which renders processes like steam reforming and the Haber-Bosch reaction economically and environmentally unviable. Nature, on the other hand, performs similar tasks efficiently at ambient temperature and pressure, exploiting gas-processing metalloenzymes (GPMs) that bind low-valent metal cofactors based on iron, nickel, molybdenum, tungsten, and sulfur. Such systems are studied to understand the biocatalytic principles of gas conversion including N2 fixation by nitrogenase and H2 production by hydrogenase as well as CO2 and CO conversion by formate dehydrogenase, carbon monoxide dehydrogenase, and nitrogenase. In this review, we emphasize the importance of the cofactor/protein interface, discussing how second and outer coordination sphere effects determine, modulate, and optimize the catalytic activity of GPMs. These may comprise ionic interactions in the second coordination sphere that shape the electron density distribution across the cofactor, hydrogen bonding changes, and allosteric effects. In the outer coordination sphere, proton transfer and electron transfer are discussed, alongside the role of hydrophobic substrate channels and protein structural changes. Combining the information gained from structural biology, enzyme kinetics, and various spectroscopic techniques, we aim toward a comprehensive understanding of catalysis beyond the first coordination sphere.
Collapse
Affiliation(s)
- Sven T Stripp
- Freie Universität Berlin, Experimental Molecular Biophysics, Berlin 14195, Germany
| | | | - Vincent Fourmond
- Laboratoire de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, Institut Microbiologie, Bioénergies et Biotechnologie, CNRS, Aix Marseille Université, Marseille 13402, France
| | - Christophe Léger
- Laboratoire de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, Institut Microbiologie, Bioénergies et Biotechnologie, CNRS, Aix Marseille Université, Marseille 13402, France
| | - Silke Leimkühler
- University of Potsdam, Molecular Enzymology, Potsdam 14476, Germany
| | - Shun Hirota
- Nara Institute of Science and Technology, Division of Materials Science, Graduate School of Science and Technology, Nara 630-0192, Japan
| | - Yilin Hu
- Department of Molecular Biology & Biochemistry, University of California, Irvine, California 92697-3900, United States
| | - Andrew Jasniewski
- Department of Molecular Biology & Biochemistry, University of California, Irvine, California 92697-3900, United States
| | - Hideaki Ogata
- Nara Institute of Science and Technology, Division of Materials Science, Graduate School of Science and Technology, Nara 630-0192, Japan
- Hokkaido University, Institute of Low Temperature Science, Sapporo 060-0819, Japan
- Graduate School of Science, University of Hyogo, Hyogo 678-1297, Japan
| | - Markus W Ribbe
- Department of Molecular Biology & Biochemistry, University of California, Irvine, California 92697-3900, United States
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| |
Collapse
|
2
|
Liedtke J, Lee CC, Tanifuji K, Jasniewski AJ, Ribbe MW, Hu Y. Characterization of a Mo-Nitrogenase Variant Containing a Citrate-Substituted Cofactor. Chembiochem 2020; 22:151-155. [PMID: 32918851 DOI: 10.1002/cbic.202000598] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 09/04/2020] [Indexed: 11/10/2022]
Abstract
Nitrogenase converts N2 to NH3 , and CO to hydrocarbons, at its cofactor site. Herein, we report a biochemical and spectroscopic characterization of a Mo-nitrogenase variant expressed in an Azotobacter vinelandii strain containing a deletion of nifV, the gene encoding the homocitrate synthase. Designated NifDKCit , the catalytic component of this Mo-nitrogenase variant contains a citrate-substituted cofactor analogue. Activity analysis of NifDKCit reveals a shift of CO reduction from H2 evolution toward hydrocarbon formation and an opposite shift of N2 reduction from NH3 formation toward H2 evolution. Consistent with a shift in the Mo K-edge energy of NifDKCit relative to that of its wild-type counterpart, EPR analysis demonstrates a broadening of the line-shape and a decrease in the intensity of the cofactor-originated S=3/2 signal, suggesting a change in the spin properties of the cofactor upon citrate substitution. These observations point to a crucial role of homocitrate in substrate reduction by nitrogenase and the possibility to tune product profiles of nitrogenase reactions via organic ligand substitution.
Collapse
Affiliation(s)
- Jasper Liedtke
- Department of Molecular Biology & Biochemistry, University of California, Irvine, 2236 McGaugh Hall, Irvine, CA 92697-3900, USA
| | - Chi Chung Lee
- Department of Molecular Biology & Biochemistry, University of California, Irvine, 2236 McGaugh Hall, Irvine, CA 92697-3900, USA
| | - Kazuki Tanifuji
- Department of Molecular Biology & Biochemistry, University of California, Irvine, 2236 McGaugh Hall, Irvine, CA 92697-3900, USA
| | - Andrew J Jasniewski
- Department of Molecular Biology & Biochemistry, University of California, Irvine, 2236 McGaugh Hall, Irvine, CA 92697-3900, USA
| | - Markus W Ribbe
- Department of Molecular Biology & Biochemistry, University of California, Irvine, 2236 McGaugh Hall, Irvine, CA 92697-3900, USA.,Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA
| | - Yilin Hu
- Department of Molecular Biology & Biochemistry, University of California, Irvine, 2236 McGaugh Hall, Irvine, CA 92697-3900, USA
| |
Collapse
|
3
|
Burén S, Jiménez-Vicente E, Echavarri-Erasun C, Rubio LM. Biosynthesis of Nitrogenase Cofactors. Chem Rev 2020; 120:4921-4968. [PMID: 31975585 PMCID: PMC7318056 DOI: 10.1021/acs.chemrev.9b00489] [Citation(s) in RCA: 106] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Indexed: 12/30/2022]
Abstract
Nitrogenase harbors three distinct metal prosthetic groups that are required for its activity. The simplest one is a [4Fe-4S] cluster located at the Fe protein nitrogenase component. The MoFe protein component carries an [8Fe-7S] group called P-cluster and a [7Fe-9S-C-Mo-R-homocitrate] group called FeMo-co. Formation of nitrogenase metalloclusters requires the participation of the structural nitrogenase components and many accessory proteins, and occurs both in situ, for the P-cluster, and in external assembly sites for FeMo-co. The biosynthesis of FeMo-co is performed stepwise and involves molecular scaffolds, metallochaperones, radical chemistry, and novel and unique biosynthetic intermediates. This review provides a critical overview of discoveries on nitrogenase cofactor structure, function, and activity over the last four decades.
Collapse
Affiliation(s)
- Stefan Burén
- Centro
de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM), Instituto
Nacional de Investigación y Tecnología Agraria
y Alimentaria (INIA), Pozuelo de Alarcón, 28223 Madrid, Spain
| | - Emilio Jiménez-Vicente
- Department
of Biochemistry, Virginia Polytechnic Institute, Blacksburg, Virginia 24061, United States
| | - Carlos Echavarri-Erasun
- Centro
de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM), Instituto
Nacional de Investigación y Tecnología Agraria
y Alimentaria (INIA), Pozuelo de Alarcón, 28223 Madrid, Spain
| | - Luis M. Rubio
- Centro
de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM), Instituto
Nacional de Investigación y Tecnología Agraria
y Alimentaria (INIA), Pozuelo de Alarcón, 28223 Madrid, Spain
| |
Collapse
|
4
|
Affiliation(s)
- Oliver Einsle
- Institute for Biochemistry, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
| | - Douglas C. Rees
- Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute, California Institute of Technology, Pasadena California 91125, United States
| |
Collapse
|
5
|
Novel bidentate oxovanadium(IV) glycolate, α-hydroxybutyrate and citrate with terpyridine and their conversions to nitrosyl products. J Inorg Biochem 2020; 208:111086. [PMID: 32353582 DOI: 10.1016/j.jinorgbio.2020.111086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 04/02/2020] [Accepted: 04/07/2020] [Indexed: 11/23/2022]
Abstract
A series of monomeric α-hydroxycarboxylato oxovanadium(IV) complexes [VO(H2cit)(tpy)]·H2O (1) (H4cit = citric acid, tpy = 2,2':6',2-terpyridine), [VO(glyc)(tpy)]·5.5H2O (2) (H2glyc = glycolic acid) and [VO(α-hbut)(tpy)]·3H2O (3) (α-H2hbut = α-hydroxybutyratic acid) have been obtained from the reactions of vanadyl sulfate with α-hydroxycarboxylates and terpyridine in acidic solutions. These complexes feature bidentate citrate, glycolate or α-hydroxybutyrate respectively. The ligand chelates to vanadium atom through α-hydroxy (in 1) or α-alkoxy (in 2 and 3) and α-carboxy groups, while β-carboxy groups of citrate in 1 are free to participate strong hydrogen bonds with neighboring citrate. With comparable chelation, 1 shares a similar V-Oα-hydroxy distance [2.168(1) Å] with that observed in FeV-cofactor [2.17 Å] [1]. Moreover, nitrosyl vanadium complexes [V(NO)(glyc)(tpy)]·3H2O (4) and [V(NO)(α-hbut)(tpy)]·4H2O (5) were obtained via reductions of synthetic solutions of 2 and 3 with hydroxylamine respectively. The terminal oxygen atoms were substituted by linear nitrosyl groups in 4 and 5. They were fully characterized by UV-vis, IR, EPR spectra, X-ray structural analyses and theoretical bond valence calculations.
Collapse
|
6
|
Newcomb MP, Lee CC, Tanifuji K, Jasniewski AJ, Liedtke J, Ribbe MW, Hu Y. A V‐Nitrogenase Variant Containing a Citrate‐Substituted Cofactor. Chembiochem 2019; 21:1742-1748. [DOI: 10.1002/cbic.201900654] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Indexed: 11/12/2022]
Affiliation(s)
- Megan P. Newcomb
- Department of Chemistry University of California, Irvine Natural Sciences II Irvine CA 92697-2025 USA
| | - Chi Chung Lee
- Department of Molecular Biology and Biochemistry University of California, Irvine 3205 McGaugh Hall Irvine CA 92697-3900 USA
| | - Kazuki Tanifuji
- Department of Molecular Biology and Biochemistry University of California, Irvine 3205 McGaugh Hall Irvine CA 92697-3900 USA
| | - Andrew J. Jasniewski
- Department of Molecular Biology and Biochemistry University of California, Irvine 3205 McGaugh Hall Irvine CA 92697-3900 USA
| | - Jasper Liedtke
- Department of Molecular Biology and Biochemistry University of California, Irvine 3205 McGaugh Hall Irvine CA 92697-3900 USA
| | - Markus W. Ribbe
- Department of Chemistry University of California, Irvine Natural Sciences II Irvine CA 92697-2025 USA
- Department of Molecular Biology and Biochemistry University of California, Irvine 3205 McGaugh Hall Irvine CA 92697-3900 USA
| | - Yilin Hu
- Department of Molecular Biology and Biochemistry University of California, Irvine 3205 McGaugh Hall Irvine CA 92697-3900 USA
| |
Collapse
|
7
|
Crystalline and solution chemistry of tetrameric and dimeric molybdenum(VI) citrato complexes. Inorganica Chim Acta 2013. [DOI: 10.1016/j.ica.2013.06.032] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
8
|
Zhou ZH, Wang H, Yu P, Olmstead MM, Cramer SP. Structure and spectroscopy of a bidentate bis-homocitrate dioxo-molybdenum(VI) complex: insights relevant to the structure and properties of the FeMo-cofactor in nitrogenase. J Inorg Biochem 2013; 118:100-6. [PMID: 23147649 PMCID: PMC3596267 DOI: 10.1016/j.jinorgbio.2012.10.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 09/30/2012] [Accepted: 10/01/2012] [Indexed: 11/26/2022]
Abstract
Direct reaction of potassium molybdate (with natural abundance Mo or enriched with (92)Mo or (100)Mo) with excess hydrolyzed homocitric acid-γ-lactone in acidic solution resulted in the isolation of a cis-dioxo bis-homocitrato molybdenum(VI) complex, K(2)[*MoO(2)(R,S-H(2)homocit)(2)]·2H(2)O (1) (*Mo=Mo, 1; (92)Mo, 2; (100)Mo, 3; H(4)homocit=homocitric acid-γ-lactone·H(2)O) and K(2)[MoO(2)((18)O-R,S-H(2)homocit)(2)]·2H(2)O (4). The complex has been characterized by elemental analysis, FT-IR, solid and solution (13)C NMR, and single crystal x-ray diffraction analysis. The molybdenum atom in (1) is quasi-octahedrally coordinated by two cis oxo groups and two bidentate homocitrate ligands. The latter coordinates via its α-alkoxy and α-carboxy groups, while the β- and γ-carboxylic acid groups remain uncomplexed, similar to the coordination mode of homocitrate in the Mo-cofactor of nitrogenase. In the IR spectra, the MoO stretching modes near 900 cm(-1) show 2-3 cm(-1) red- and blue-shifts for the (92)Mo-complex (2) and (100)Mo-complex (3) respectively compared with the natural abundance version (1). At lower frequencies, bands at 553 and 540 cm(-1) are assigned to ν(Mo-O) vibrations involving the alkoxide ligand. At higher frequencies, bands in the 1700-1730 cm(-1) region are assigned to stretching modes of protonated carboxylates. In addition, a band at 1675 cm(-1) was observed that may be analogous to a band seen at 1677 cm(-1) in nitrogenase photolysis studies. The solution behavior of (1) in D(2)O was probed with (1)H and (13)C NMR spectra. An obvious dissociation of homocitrate was found, even though bound to the high valent Mo(VI). This suggests the likely lability of coordinated homocitrate in the FeMo-cofactor with its lower valence Mo(IV).
Collapse
Affiliation(s)
- Zhao-Hui Zhou
- Department of Chemistry, University of California, Davis, CA 95616
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
- State Key Laboratory for Physical Chemistry of the Solid Surfaces, Xiamen University, Xiamen 361005, China
| | - Hongxin Wang
- Department of Chemistry, University of California, Davis, CA 95616
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Ping Yu
- NMR Facility, University of California, Davis, CA 95616
| | | | - Stephen P. Cramer
- Department of Chemistry, University of California, Davis, CA 95616
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| |
Collapse
|
9
|
Dance I. The controlled relay of multiple protons required at the active site of nitrogenase. Dalton Trans 2012; 41:7647-59. [DOI: 10.1039/c2dt30518f] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
10
|
Hallenbeck PC, George GN, Prince RC, Thorneley RNF. Characterization of a modified nitrogenase Fe protein from Klebsiella pneumoniae in which the 4Fe4S cluster has been replaced by a 4Fe4Se cluster. J Biol Inorg Chem 2009; 14:673-82. [PMID: 19234722 DOI: 10.1007/s00775-009-0480-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Accepted: 02/06/2009] [Indexed: 11/25/2022]
Abstract
The Azotobacter vinelandii nifS gene product has been used with selenocysteine to reconstitute Klebsiella pneumoniae nitrogenase Fe protein. Chemical analysis and extended X-ray absorption fine structure (EXAFS) spectroscopy show that the 4Fe4S cluster present in the native protein is replaced by a 4Fe4Se cluster. As well, EXAFS spectroscopy shows that the bond lengths to the cysteine thiolate ligands shrink by 0.05 A (from 2.28 to 2.23 A) upon reduction, whereas the Fe-Fe distance is essentially unchanged. Thus, the core of the 4Fe4Se cluster remains essentially static on reduction, whilst the external cysteine thiolate ligands are pulled in towards the cluster. Compared with native (S)-Fe protein, the (Se)-Fe protein has a 20-fold increased rate of MgATP-induced Fe chelation, a sixfold decreased specific activity for acetylene reduction, a fivefold decreased rate of MgATP-dependent electron transfer from (Se)-Fe protein to MoFe protein, and a fourfold increase in the ATP to 2e (-) ratio. The high ATP to 2e (-) ratio and decreased specific activity are consistent with a lower rate of dissociation of oxidized (Se)-Fe protein from reduced MoFe protein. Thus, the relatively small adjustments in the Fe protein structure necessary to accommodate the 4Fe4Se cluster are transmitted both to adjacent residues that dock at the surface of the MoFe protein and to the ATP hydrolysis sites located approximately 19 A away.
Collapse
Affiliation(s)
- Patrick Clark Hallenbeck
- Département de Microbiologie et Immunologie, Université de Montréal, Succursale Centre-ville, Montreal, QC, Canada.
| | | | | | | |
Collapse
|
11
|
Abstract
The iron-molybdenum cofactor (FeMo-co), located at the active site of the molybdenum nitrogenase, is one of the most complex metal cofactors known to date. During the past several years, an intensive effort has been made to purify the proteins involved in FeMo-co synthesis and incorporation into nitrogenase. This effort is starting to provide insights into the structures of the FeMo-co biosynthetic intermediates and into the biochemical details of FeMo-co synthesis.
Collapse
Affiliation(s)
- Luis M Rubio
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.
| | | |
Collapse
|
12
|
Abstract
The iron-molybdenum cofactor (FeMo-co), located at the active site of the molybdenum nitrogenase, is one of the most complex metal cofactors known to date. During the past several years, an intensive effort has been made to purify the proteins involved in FeMo-co synthesis and incorporation into nitrogenase. This effort is starting to provide insights into the structures of the FeMo-co biosynthetic intermediates and into the biochemical details of FeMo-co synthesis.
Collapse
Affiliation(s)
- Luis M Rubio
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.
| | | |
Collapse
|
13
|
Dos Santos PC, Dean DR, Hu Y, Ribbe MW. Formation and insertion of the nitrogenase iron-molybdenum cofactor. Chem Rev 2004; 104:1159-73. [PMID: 14871152 DOI: 10.1021/cr020608l] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
14
|
Durrant MC. An Atomic Level Model for the Interactions of Molybdenum Nitrogenase with Carbon Monoxide, Acetylene, and Ethylene. Biochemistry 2004; 43:6030-42. [PMID: 15147187 DOI: 10.1021/bi036300l] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A combination of density functional theory and molecular mechanics calculations has been used to study the possible interactions of CO, C(2)H(2), and C(2)H(4) with the central Fe and terminal Mo sites of the iron-molybdenum cofactor of nitrogenase. The most favorable binding mode for CO on the central section of the FeMoco appears to be end-on to a single Fe and results in a change from high to low spin for the ligating Fe atom. If a coordination site for CO is available on the Mo, this becomes the preferred CO binding site. Calculated nu(CO) infrared frequencies are compared with the experimental values given in the literature. C(2)H(2) binds weakly in a side-on orientation to a single Fe site; addition of a single H(+)/e(-) couple to the substrate results in spontaneous migration of the resulting -CH=CH(2) group from Fe to a central S atom of the cofactor. Further reduction liberates C(2)H(4) or alternatively can give an S=CHCH(3) intermediate, which then goes on to produce C(2)H(6). A model for C(2)H(2) reduction by nitrogenase is proposed, based on the results of the calculations and the extensive literature on this process.
Collapse
Affiliation(s)
- Marcus C Durrant
- Computational Biology Group, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK.
| |
Collapse
|
15
|
McLean PA, True A, Nelson MJ, Lee HI, Hoffman BM, Orme-Johnson WH. Effects of substrates (methyl isocyanide, C2H2) and inhibitor (CO) on resting-state wild-type and NifV(-)Klebsiella pneumoniae MoFe proteins. J Inorg Biochem 2003; 93:18-32. [PMID: 12538049 DOI: 10.1016/s0162-0134(02)00580-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We report the use of electron nuclear double resonance (ENDOR) spectroscopy to examine how the metal sites in the FeMo-cofactor cluster of the resting nitrogenase MoFe protein respond to addition of the substrates acetylene and methyl isocyanide and the inhibitor carbon monoxide. 1H, 57Fe and 95Mo ENDOR measurements were performed on the wild-type and the NifV(-)proteins from Klebsiella pneumoniae. Among the molecules tested, only the addition of acetylene to either protein induced widespread changes in the 57Fe ENDOR spectra. Acetylene also induced increases in intensity from unresolved protons in the proton ENDOR spectra. Thus we conclude that acetylene may bind to the resting-state MoFe protein to perturb the FeMo-cofactor environment. On the other hand, the present results show that methyl isocyanide and carbon monoxide do not substantially alter the FeMo cofactor's geometric and electronic structures. We interpret this as lack of interaction between those two molecules and the FeMo cofactor in the resting state MoFe protein. Thus, although it is generally accepted that substrates or inhibitors bind to the FeMo-cofactor only under turnover condition, this work provides evidence that at least one substrate can perturb the active site of nitrogenase under non-catalytic conditions.
Collapse
Affiliation(s)
- Paul A McLean
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | | | | | | | | |
Collapse
|
16
|
Rangaraj P, Ludden PW. Accumulation of 99Mo-containing iron-molybdenum cofactor precursors of nitrogenase on NifNE, NifH, and NifX of Azotobacter vinelandii. J Biol Chem 2002; 277:40106-11. [PMID: 12176981 DOI: 10.1074/jbc.m204581200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The biosynthesis of the iron-molybdenum cofactor (FeMo-co) of nitrogenase was investigated using the purified in vitro FeMo-co synthesis system and 99Mo. The purified system involves the addition of all components that are known to be required for FeMo-co synthesis in their purified forms. Here, we report the accumulation of a 99Mo-containing FeMo-co precursor on NifNE. Apart from NifNE, NifH and NifX also accumulate 99Mo label. We present evidence that suggests NifH may serve as the entry point for molybdenum incorporation into the FeMo-co biosynthetic pathway. We also present evidence suggesting a role for NifX in specifying the organic acid moiety of FeMo-co.
Collapse
Affiliation(s)
- Priya Rangaraj
- Department of Biochemistry and the Center for the Study of Nitrogen Fixation, College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | | |
Collapse
|
17
|
Mayer SM, Gormal CA, Smith BE, Lawson DM. Crystallographic analysis of the MoFe protein of nitrogenase from a nifV mutant of Klebsiella pneumoniae identifies citrate as a ligand to the molybdenum of iron molybdenum cofactor (FeMoco). J Biol Chem 2002; 277:35263-6. [PMID: 12133839 DOI: 10.1074/jbc.m205888200] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The x-ray crystal structure of NifV(-) Klebsiella pneumoniae nitrogenase MoFe protein (NifV(-) Kp1) has been determined and refined to a resolution of 1.9 A. This is the first structure for a nitrogenase MoFe protein with an altered cofactor. Moreover, it is the first direct evidence that the organic acid citrate is not just present, but replaces homocitrate as a ligand to the molybdenum atom of the iron molybdenum cofactor (FeMoco). Subsequent refinement of the structure revealed that the citrate was present at reduced occupancy.
Collapse
Affiliation(s)
- Suzanne M Mayer
- Department of Biological Chemistry, John Innes Centre, Norwich NR4 7UH, United Kingdom
| | | | | | | |
Collapse
|
18
|
Allen RM, Roll JT, Rangaraj P, Shah VK, Roberts GP, Ludden PW. Incorporation of molybdenum into the iron-molybdenum cofactor of nitrogenase. J Biol Chem 1999; 274:15869-74. [PMID: 10336491 DOI: 10.1074/jbc.274.22.15869] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The biosynthesis of the iron-molybdenum cofactor (FeMo-co) of dinitrogenase was investigated using 99Mo to follow the incorporation of Mo into precursors. 99Mo label accumulates on dinitrogenase only when all known components of the FeMo-co synthesis system, NifH, NifNE, NifB-cofactor, homocitrate, MgATP, and reductant, are present. Furthermore, 99Mo label accumulates only on the gamma protein, which has been shown to serve as a chaperone/insertase for the maturation of apodinitrogenase when all known components are present. It appears that only completed FeMo-co can accumulate on the gamma protein. Very little FeMo-co synthesis was observed when all known components are used in purified forms, indicating that additional factors are required for optimal FeMo-co synthesis. 99Mo did not accumulate on NifNE under any conditions tested, suggesting that Mo enters the pathway at some other step, although it remains possible that a Mo-containing precursor of FeMo-co that is not sufficiently stable to persist during gel electrophoresis occurs but is not observed. 99Mo accumulates on several unidentified species, which may be the additional components required for FeMo-co synthesis. The molybdenum storage protein was observed and the accumulation of 99Mo on this protein required nucleotide.
Collapse
Affiliation(s)
- R M Allen
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | | | | | | | | | | |
Collapse
|
19
|
Smith BE. Structure, Function, and Biosynthesis of the Metallosulfur Clusters in Nitrogenases. ADVANCES IN INORGANIC CHEMISTRY 1999. [DOI: 10.1016/s0898-8838(08)60078-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
20
|
Affiliation(s)
- Barbara K. Burgess
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92717-3900, and Nitrogen Fixation Laboratory, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, U.K
| | | |
Collapse
|
21
|
Allen RM, Chatterjee R, Madden MS, Ludden PW, Shah VK. Biosynthesis of the iron-molybdenum cofactor of nitrogenase. Crit Rev Biotechnol 1994; 14:225-49. [PMID: 7954845 DOI: 10.3109/07388554409079834] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The iron-molybdenum cofactor (FeMo-co) of nitrogenase is a unique molybdenum-containing prosthetic group that has been proposed to form an integral part of the active site of dinitrogenase. In Klebsiella pneumoniae, at least six nif (nitrogen fixation) gene products are required for the biosynthesis of FeMo-co, including NIFB, NIFNE, NIFH, NIFQ, and NIFV. An in vitro system for the synthesis of FeMo-co, which requires MgATP, molybdate, homocitrate, and at least the products of nifN, E, B, and H, has provided an enzymatic assay for the purification of many of the gene products required for FeMo-co biosynthesis. Although the structure of the cofactor has been solved recently, much about the biosynthetic pathway remains unknown. This article reviews what is known about the various components required for FeMo-co biosynthesis.
Collapse
Affiliation(s)
- R M Allen
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison
| | | | | | | | | |
Collapse
|
22
|
Madden MS, Paustian TD, Ludden PW, Shah VK. Effects of homocitrate, homocitrate lactone, and fluorohomocitrate on nitrogenase in NifV- mutants of Azotobacter vinelandii. J Bacteriol 1991; 173:5403-5. [PMID: 1885520 PMCID: PMC208251 DOI: 10.1128/jb.173.17.5403-5405.1991] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Azotobacter vinelandii DJ71, which contains a mutation in the nifV gene, was derepressed for nitrogenase in the presence of homocitrate. When dinitrogenase was isolated from this culture, it was found to be identical to the wild-type dinitrogenase. However, when the same NifV- strain was derepressed in the presence of erythrofluorohomocitrate, a homocitrate analog which produces a nitrogenase with wild-type properties in vitro, the isolated dinitrogenase was characteristic of the NifV- enzyme. These data show that homocitrate, but not fluorohomocitrate, is utilized by NifV- mutant cells. Fluorohomocitrate does not inhibit the uptake of homocitrate because the wild-type phenotype resulted when both compounds were added to the medium during nitrogenase derepression. Homocitrate lactone failed to cure the NifV- phenotype.
Collapse
Affiliation(s)
- M S Madden
- Department of Biochemistry, University of Wisconsin-Madison 53706
| | | | | | | |
Collapse
|
23
|
|
24
|
Wang SZ, Dean DR, Chen JS, Johnson JL. The N-terminal and C-terminal portions of NifV are encoded by two different genes in Clostridium pasteurianum. J Bacteriol 1991; 173:3041-6. [PMID: 2022611 PMCID: PMC207896 DOI: 10.1128/jb.173.10.3041-3046.1991] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The nifV gene products from Azotobacter vinelandii and Klebsiella pneumoniae share a high level of primary sequence identity and are proposed to catalyze the synthesis of homocitrate. While searching for potential nif (nitrogen fixation) genes within the genomic region located downstream from the nifN-B gene of Clostridium pasteurianum, we observed two open reading frames (ORFs) whose deduced amino acid sequences exhibit nonoverlapping sequence identity to different portions of the nifV gene products from A. vinelandii and K. pneumoniae. Conserved regions were located between the C-terminal 195 amino acid residues of the first ORF and the C-terminal portion of the nifV gene product and between the entire sequence of the second ORF (269 amino acid residues) and the N-terminal portion of the nifV gene product. We therefore designated the first ORF nifV omega and the second ORF nifV alpha. The deduced amino acid sequences of nifV omega and nifV alpha were also found to have sequence similarity when compared with the primary sequence of the leuA gene product from Salmonella typhimurium, which encodes alpha-isopropylmalate synthase. Marker rescue experiments were performed by recombining nifV omega and nifV alpha from C. pasteurianum, singly and in combination, into the genome of an A. vinelandii mutant strain which has an insertion and a deletion mutation located within its nifV gene. A NifV+ phenotype was obtained only when both the C. pasteurianum nifV omega and nifV alpha genes were introduced into the chromosome of this mutant strain. These results suggest that the nifV omega and nifV alpha genes encode separate domains, both of which are required for homocitrate synthesis in C. pasteurianum.
Collapse
Affiliation(s)
- S Z Wang
- Department of Anaerobic Microbiology, Virginia Polytechnic Institute and State University, Blacksburg 24061
| | | | | | | |
Collapse
|
25
|
Howard JB, Rees DC. Perspectives on non-heme iron protein chemistry. ADVANCES IN PROTEIN CHEMISTRY 1991; 42:199-280. [PMID: 1793006 DOI: 10.1016/s0065-3233(08)60537-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- J B Howard
- Department of Biochemistry, University of Minnesota School of Medicine, Minneapolis 55455
| | | |
Collapse
|
26
|
Lowe DJ, Fisher K, Thorneley RN. Klebsiella pneumoniae nitrogenase. Mechanism of acetylene reduction and its inhibition by carbon monoxide. Biochem J 1990; 272:621-5. [PMID: 2268290 PMCID: PMC1149753 DOI: 10.1042/bj2720621] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The electron flux through the MoFe-protein of nitrogenase from Klebsiella pneumoniae determines the absolute and relative rates of 2H+ reduction to H2 and acetylene (C2H2) reduction to ethylene (C2H4) at saturating levels of reductant (Na2S2O4) and MgATP. High electron flux, induced by a high Fe-protein (Kp2)/MoFe protein (Kp1) ratio, favours C2H2 reduction. These data can be explained if ethylene, the two-electron reduction product of C2H2, is not released until three electrons have been transferred from Kp2 to Kp1. This explanation is also consistent with a pre-steady-state lag phase for C2H4 formation of 250 ms observed when functioning enzyme is quenched with acid. Electron flux through nitrogenase is inhibited by C2H2 at high protein concentrations. This is because the association rate between Kp1 and oxidized Kp2 is enhanced by C2H2, leading to an increased steady-state concentration of the inhibitory complex Kp2oxKp1C2H2. This effect is not relieved by CO. Thus CO and C2H2 (or C2H4) must be bound at the same time to distinct sites, presumably at Mo or Fe centres, on the enzyme.
Collapse
Affiliation(s)
- D J Lowe
- AFRC Institute of Plant Science Research, University of Sussex, Brighton, U.K
| | | | | |
Collapse
|
27
|
Imperial J, Hoover TR, Madden MS, Ludden PW, Shah VK. Substrate reduction properties of dinitrogenase activated in vitro are dependent upon the presence of homocitrate or its analogues during iron-molybdenum cofactor synthesis. Biochemistry 1989; 28:7796-9. [PMID: 2514794 DOI: 10.1021/bi00445a040] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
(R)-2-Hydroxy-1,2,4-butanetricarboxylic acid [(R)-homocitrate] has been has been recently reported to be an integral constituent of the otherwise thought to be inorganic iron-molybdenum cofactor of dinitrogenase [Hoover, T.R., Imperial, J., Ludden, P.W., & Shah, V.K. (1989) Biochemistry 28,2768-2771]. Different organic acids can substitute for homocitrate in an in vitro system for iron-molybdenum cofactor synthesis and incorporation into dinitrogenase [Hoover, T.R., Imperial, J., Ludden, P.W., & Shah, V. K. (1988) Biochemistry 27, 3647-3652]. Dinitrogenase activated with homocitrate-FeMo-co was able to reduce dinitrogen, acetylene, and protons efficiently. Homoisocitrate and isocitrate dinitrogenases did not reduce dinitrogen or acetylene, but showed very high proton reduction activities. Citrate and citramalate dinitrogenases had very low dinitrogen reduction activities and intermediate acetylene and proton reduction activities. CO inhibited proton reduction in both these cases but not in the case of dinitrogenases activated with other homocitrate analogues. By use of these and other commercially available homocitrate analogues in the in vitro system, the structural features of the homocitrate molecule absolutely required for the synthesis of a catalytically competent iron-molybdenum cofactor were determined to be the hydroxyl group, the 1- and 2-carboxyl groups, and the R configuration of the chiral center. The stringency of the structural requirements was dependent on the nitrogenase substrate used for the assay, with dinitrogen having the most stringent requirements followed by acetylene and protons.
Collapse
Affiliation(s)
- J Imperial
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706
| | | | | | | | | |
Collapse
|
28
|
Liang J, Burris RH. N2O reduction and HD formation by nitrogenase from a nifV mutant of Klebsiella pneumoniae. J Bacteriol 1989; 171:3176-80. [PMID: 2656643 PMCID: PMC210033 DOI: 10.1128/jb.171.6.3176-3180.1989] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Dinitrogenase from a nifV mutant of Klebsiella pneumoniae contains an altered form of iron-molybdenum cofactor (FeMoco) that lacks a biologically active homocitric acid molecule. Change in the composition of FeMoco led to substantial variation in the kinetics of nitrogenase action. The KmS of the mutant enzyme for N2 and N2O were 0.244 and 0.175 atm (24,714 and 17,726 kPa), respectively. The km for N2 was higher and the Km for N2O was lower than that for the wild-type enzyme. The mutant enzyme was ineffective in N2 fixation, in N2O reduction, and in HD formation, as indicated by the low Vmax of these reactions with saturating levels of substrate and under conditions of saturating electron flux. These observations provide further support for the concept that N2, N2O, and D2 interact with the same form of dinitrogenase. H2 evolution by the mutant enzyme is only partially inhibited by CO. Observation that different numbers of electrons are stored in CO-inhibited than in noninhibited dinitrogenase before H2 is released suggests that the mutant enzyme has more sites responsible for H2 evolution than the wild-type enzyme, whose H2 evolution is not inhibited by CO.
Collapse
Affiliation(s)
- J Liang
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53706
| | | |
Collapse
|
29
|
Gemoets JP, Bravo M, McKenna CE, Leigh GJ, Smith BE. Reduction of cyclopropene by NifV- and wild-type nitrogenases from Klebsiella pneumoniae. Biochem J 1989; 258:487-91. [PMID: 2650681 PMCID: PMC1138387 DOI: 10.1042/bj2580487] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The nitrogenase from wild-type Klebsiella pneumoniae reduces cyclopropene to cyclopropane and propene in the ratio 1:2 at pH 7.5. We show in this paper that the nitrogenase from a nifV mutant of K. pneumoniae also reduces cyclopropene to cyclopropane and propene, but the ratio of products is now 1:1.4. However, both nitrogenases exhibit the same Km for cyclopropene (2.1 x 10(4) +/- 0.2 x 10(4) Pa), considerably more than the Km for the analogous reaction with Azotobacter vinelandii nitrogenase under the same conditions (5.1 x 10(3) Pa). Analysis of the data shows that the different product ratio arises from the slower production of propene compared with cyclopropane by the mutant nitrogenase. During turnover, both nitrogenases use a large proportion of the electron flux for H2 production. CO inhibits the reduction of cyclopropene by both K. pneumoniae proteins, but the mutant nitrogenase exhibits 50% inhibition at approx. 10 Pa, whereas the corresponding value for the wild-type nitrogenase is approx. 110 Pa. However, H2 evolution by the mutant enzyme is much less affected than is cyclopropene reduction. CO inhibition of cyclopropene reduction by the nitrogenases coincides with a relative increase in H2 evolution, so that in the wild-type (but not the mutant) the electron flux is approximately maintained. The cyclopropane/propene production ratios are little affected by the presence of CO within the pressure ranges studied at least up to 50% inhibition.
Collapse
Affiliation(s)
- J P Gemoets
- Department of Chemistry, University of Southern California, Los Angeles 90089-0744
| | | | | | | | | |
Collapse
|
30
|
Dilworth MJ, Eady RR, Eldridge ME. The vanadium nitrogenase of Azotobacter chroococcum. Reduction of acetylene and ethylene to ethane. Biochem J 1988; 249:745-51. [PMID: 3162672 PMCID: PMC1148769 DOI: 10.1042/bj2490745] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
1. The vanadium (V-) nitrogenase of Azobacter chroococcum transfers up to 7.4% of the electrons used in acetylene (C2H2) reduction for the formation of ethane (C2H6). The apparent Km for C2H2 (6 kPa) is the same for either ethylene (C2H4) or ethane (C2H6) formation and much higher than the reported Km values for C2H2 reduction to C2H4 by molybdenum (Mo-) nitrogenases. Reduction of C2H2 in 2H2O yields predominantly [cis-2H2]ethylene. 2. The ratio of electron flux yielding C2H6 to that yielding C2H4 (the C2H6/C2H4 ratio) is increased by raising the ratio of Fe protein to VFe protein and by increasing the assay temperature up to at least 40 degrees C. pH values above 7.5 decrease the C2H6/C2H4 ratio. 3. C2H4 and C2H6 formation from C2H2 by V-nitrogenase are not inhibited by H2. CO inhibits both processes much less strongly than it inhibits C2H4 formation from C2H2 with Mo-nitrogenase. 4. Although V-nitrogenase also catalyses the slow CO-sensitive reduction of C2H4 to C2H6, free C2H4 is not an intermediate in C2H6 formation from C2H2. 5. Propyne (CH3C identical to CH) is not reduced by the V-nitrogenase. 6. Some implications of these results for the mechanism of C2H6 formation by the V-nitrogenase are discussed.
Collapse
Affiliation(s)
- M J Dilworth
- AFRC Unit of Nitrogen Fixation, University of Sussex, Brighton, U.K
| | | | | |
Collapse
|
31
|
Ashby GA, Dilworth MJ, Thorneley RN. Klebsiella pneumoniae nitrogenase. Inhibition of hydrogen evolution by ethylene and the reduction of ethylene to ethane. Biochem J 1987; 247:547-54. [PMID: 3322266 PMCID: PMC1148448 DOI: 10.1042/bj2470547] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Ethylene (C2H4) inhibited H2 evolution by the Mo-containing nitrogenase of Klebsiella pneumoniae. The extent of inhibition depended on the electron flux determined by the ratio of Fe protein (Kp2) to MoFe protein (Kp1) with KiC2H4 = 409 kPa ([Kp2]/[Kp1] = 22:1) and KC2H4i = 88 kPa ([Kp1]/[Kp2] = 21:1) at 23 degrees C at pH 7.4. At [Kp2]/[Kp1] = 1:1, inhibition was minimal with C2H4 (101 kPa). Extrapolation of data obtained when C2H4 was varied from 60 to 290 kPa indicates that at infinite pressure of C2H4 total inhibition of H2 evolution should occur. C2H4 inhibited concomitant S2O4(2-) oxidation to the same extent that it inhibited H2 evolution. Although other inhibitors of total electron flux such as CN- and CH3NC uncouple MgATP hydrolysis from electron transfer, C2H4 did not affect the ATP/2e ratio. Inhibition of H2 evolution by C2H4 was not relieved by CO. C2H4 was reduced to C2H6 at [Kp2]/[Kp1] ratios greater than or equal to 5:1 in a reaction that accounted for no more than 1% of the total electron flux. These data are discussed in terms of the chemistry of alkyne and alkene reduction on transition-metal centres.
Collapse
Affiliation(s)
- G A Ashby
- A.F.R.C. Unit of Nitrogen Fixation, University of Sussex, Brighton, U.K
| | | | | |
Collapse
|
32
|
Hoover TR, Shah VK, Roberts GP, Ludden PW. nifV-dependent, low-molecular-weight factor required for in vitro synthesis of iron-molybdenum cofactor of nitrogenase. J Bacteriol 1986; 167:999-1003. [PMID: 3017921 PMCID: PMC215971 DOI: 10.1128/jb.167.3.999-1003.1986] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The molybdate- and ATP-dependent in vitro synthesis of the iron-molybdenum cofactor of nitrogenase requires a low-molecular-weight factor. The factor is present in extracts of nitrogen fixation-derepressed cultures of Klebsiella pneumoniae and Azotobacter vinelandii, but not in extracts of repressed cultures of these bacteria. Analysis of K. pneumoniae Nif mutants has indicated that the nifV gene product is the only nif protein (besides nifA) necessary for the synthesis and accumulation of the factor. The factor is stable to oxygen, temperatures below 120 degrees C, and extremely acidic and basic conditions. The activity of the factor was completely destroyed by dry ashing or digestion with sulfuric acid. The factor has been partially purified by filtration through an Amicon PM-10 DIAFLO membrane and chromatography on DEAE-cellulose, hydroxylapatite, silica gel, and Sephadex G-25.
Collapse
|
33
|
Shah VK, Imperial J, Ugalde RA, Ludden PW, Brill WJ. In vitro synthesis of the iron-molybdenum cofactor of nitrogenase. Proc Natl Acad Sci U S A 1986; 83:1636-40. [PMID: 3006060 PMCID: PMC323138 DOI: 10.1073/pnas.83.6.1636] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Molybdate- and ATP-dependent in vitro synthesis of the iron-molybdenum cofactor (FeMo-co) of nitrogenase requires the protein products of at least the nifB, nifN, and nifE genes. Extracts of FeMo-co-negative mutants of Klebsiella pneumoniae and Azotobacter vinelandii with lesions in different genes can be complemented for FeMo-co synthesis. Both K. pneumoniae and A. vinelandii dinitrogenase (component I) deficient in FeMo-co can be activated by FeMo-co synthesized in vitro. Properties of the partially purified dinitrogenase activated by FeMo-co synthesized in vitro were comparable to those of dinitrogenase from the wild-type organism; e.g., ratios of acetylene- to nitrogen-reduction activities, as well as those of acetylene reduction activities to EPR spectrum peak height at g = 3.65, were very similar. A. vinelandii mutants UW45 and CA30 have mutations in a gene functionally equivalent to nifB of K. pneumoniae.
Collapse
|
34
|
Howard KS, McLean PA, Hansen FB, Lemley PV, Koblan KS, Orme-Johnson WH. Klebsiella pneumoniae nifM gene product is required for stabilization and activation of nitrogenase iron protein in Escherichia coli. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)36161-6] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
35
|
Hawkes TR, McLean PA, Smith BE. Nitrogenase from nifV mutants of Klebsiella pneumoniae contains an altered form of the iron-molybdenum cofactor. Biochem J 1984; 217:317-21. [PMID: 6320803 PMCID: PMC1153212 DOI: 10.1042/bj2170317] [Citation(s) in RCA: 175] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
When the iron-molybdenum cofactor (FeMoco) was extracted from the MoFe protein of nitrogenase from a nifV mutant of Klebsiella pneumoniae and combined with the FeMoco-deficient MoFe protein from a nifB mutant, the resultant MoFe protein exhibited the NifV phenotype, i.e. in combination with wild-type Fe protein it exhibited poor N2-fixation activity and its H2-evolution activity was inhibited by CO. These data provide strong evidence that FeMoco contains the active site of nitrogenase. The metal contents and e.p.r. properties of FeMoco from wild-type and nifV mutants of K. pneumoniae are very similar.
Collapse
|