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Role for the nitrogenase MoFe protein alpha-subunit in FeMo-cofactor binding and catalysis. 1990

D J Scott, and H D May, and W E Newton, and K E Brigle, and D R Dean
Western Regional Research Center, USDA-ARS, Albany, California 94710.

Two components constitute Mo-dependent nitrogenase (EC 1.18.6.1)--the Fe protein (a homodimer encoded by nifH) and the MoFe protein (an alpha 2 beta 2 tetramer encoded by nifDK). The MoFe protein provides the substrate-binding site and probably contains six prosthetic groups of two types--four Fe-S centres and two Fe- and Mo-containing cofactors. To determine the distribution and catalytic function of these metalloclusters, we and others are attempting to change the catalytic and spectroscopic features of nitrogenase by substituting specific amino acids targeted as potential metallocluster ligands, particularly those to the FeMo-cofactor, which is responsible for the biologically unique electron paramagnetic resonance signal (S = 3/2) of nitrogenase, and is believed to be the N2-reducing site. Here we describe mutant strains of Azotobacter vinelandii that have single amino-acid substitutions within the MoFe protein alpha-subunit. These substitutions alter both substrate-reduction properties and the unique electron paramagnetic resonance signal, indicating that the FeMo-cofactor is associated with both the alpha-subunit and the substrate-reducing site.

UI MeSH Term Description Entries
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D008983 Molybdoferredoxin A non-heme iron-sulfur protein isolated from Clostridium pasteurianum and other bacteria. It is a component of NITROGENASE, which is active in nitrogen fixation, and consists of two subunits with molecular weights of 59.5 kDa and 50.7 kDa, respectively. Molybdenum-Iron Protein,FeMo Cofactor,Iron-Molybdenum Cofactor,MoFe Protein,Iron Molybdenum Cofactor,Molybdenum Iron Protein
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D009586 Nitrogen Fixation The process in certain BACTERIA; FUNGI; and CYANOBACTERIA converting free atmospheric NITROGEN to biologically usable forms of nitrogen, such as AMMONIA; NITRATES; and amino compounds. Diazotrophy,Diazotrophic Activity,Dinitrogen Fixation,N2 Fixation,Activities, Diazotrophic,Activity, Diazotrophic,Diazotrophic Activities,Fixation, Dinitrogen,Fixation, N2,Fixation, Nitrogen
D009591 Nitrogenase An enzyme system that catalyzes the fixing of nitrogen in soil bacteria and blue-green algae (CYANOBACTERIA). EC 1.18.6.1. Dinitrogenase,Vanadium Nitrogenase,Nitrogenase, Vanadium
D011485 Protein Binding The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments. Plasma Protein Binding Capacity,Binding, Protein
D004578 Electron Spin Resonance Spectroscopy A technique applicable to the wide variety of substances which exhibit paramagnetism because of the magnetic moments of unpaired electrons. The spectra are useful for detection and identification, for determination of electron structure, for study of interactions between molecules, and for measurement of nuclear spins and moments. (From McGraw-Hill Encyclopedia of Science and Technology, 7th edition) Electron nuclear double resonance (ENDOR) spectroscopy is a variant of the technique which can give enhanced resolution. Electron spin resonance analysis can now be used in vivo, including imaging applications such as MAGNETIC RESONANCE IMAGING. ENDOR,Electron Nuclear Double Resonance,Electron Paramagnetic Resonance,Paramagnetic Resonance,Electron Spin Resonance,Paramagnetic Resonance, Electron,Resonance, Electron Paramagnetic,Resonance, Electron Spin,Resonance, Paramagnetic
D005288 Ferredoxins Iron-containing proteins that transfer electrons, usually at a low potential, to flavoproteins; the iron is not present as in heme. (McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed) Ferredoxin,Ferredoxin I,Ferredoxin II,Ferredoxin III
D005798 Genes, Bacterial The functional hereditary units of BACTERIA. Bacterial Gene,Bacterial Genes,Gene, Bacterial
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein

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