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Literature summary for 1.18.6.1 extracted from

  • Igarashi, R.Y.; Seefeldt, L.C.
    Nitrogen fixation: the mechanism of the Mo-dependent nitrogenase (2003), Crit. Rev. Biochem. Mol. Biol., 38, 351-384.
    View publication on PubMed

Crystallization (Commentary)

Crystallization (Comment) Organism
crystal structure analysis of the iron protein, and of the MoFe protein Azotobacter vinelandii

Protein Variants

Protein Variants Comment Organism
D125E site-directed mutagenesis, mutation alters the properties of the MgATP2- binding site with bound MgADP Azotobacter vinelandii
G69S random mutagenesis, beta-subunit residue mutant of the MoFe protein shows highly decreased affinity for acetylene, acetylene inhibits the mutants nitrogen reduction activity in a competitive mode in contrast to the wild-type enzyme Azotobacter vinelandii
K15Q site-directed mutagenesis, mutation inhibits the communication of the [4Fe4S] cluster with the MgATP2- binding site Azotobacter vinelandii
additional information deletion of nifH results in an enzyme complex with a MoFe protein exhibiting altered redox properties and no EPR signal, a Fe protein Lys127 deletion mutant mimics the MgATP-bound-conformation and inhibits nucleotide hydrolyzing activity, formation of nondissociating complex with the MoFe protein Azotobacter vinelandii
S188C site-directed mutagenesis, mutation of a residue within the P-cluster of the beta-subunit, alters the EPR signal of the MoFe protein Azotobacter vinelandii

Inhibitors

Inhibitors Comment Organism Structure
Acetylene noncompetitive inhibition of nitrogen reduction, Gly69 is important Azotobacter vinelandii
beryllium fluoride inhibits by trapping of a stable Fe protein-MoFe protein nitrogenase complex Azotobacter vinelandii
CO strong inhibition, binding site and inhibition mechanism Azotobacter vinelandii
cyanide
-
Azotobacter vinelandii
tetrafluoroaluminate inhibits by trapping of a stable Fe protein-MoFe protein nitrogenase complex, binds to the Fe protein Azotobacter vinelandii

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
additional information
-
additional information redox properties of metal clusters and P-cluster, overview Azotobacter vinelandii

Metals/Ions

Metals/Ions Comment Organism Structure
Iron dependent on, the enzyme complex contains a molybdenum-iron, a tetramer with 2 different subunits and 4 organo-metallic clusters, i.e. 2 iron-molybdenum cofactors and 2 P-clusters encoded by the genes nifD and nifK, the enzyme complex contains also a dimeric iron protein, encoded by the nifH gene, with a [4Fe4S] cluster between subunits and 2 MgATP binding sites, mechanism of electron transfer between metal clusters, mechanism of switch I and II, complex formation with the MoFe protein, also between different species, overview Azotobacter vinelandii
Mg2+ required for ATP binding and MgATP hydrolysis, 2 MgATP binding sites on the iron protein connected via residues K15, D125, and C132, binding changes the conformation and the redox status of the [4Fe4S] cluster of the iron protein, mechanism, overview Azotobacter vinelandii
Molybdenum dependent on, the enzyme complex contains a molybdenum-iron, a tetramer with 2 different subunits and 4 organo-metallic clusters, i.e. 2 iron-molybdenum cofactors [7Fe-Mo-9S-X-homocitrate] and 2 P-clusters [8Fe-7S], mechanism of electron transfer between metal clusters, complex formation with the Fe protein, also between different species, overview Azotobacter vinelandii
additional information structure catalytic role, and mechanism of the P-cluster, part of the MoFe protein, which has a role in immediate electron acceptance from the Fe protein Azotobacter vinelandii

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
additional information Azotobacter vinelandii the activity of the enzyme complex is regulated by specific interactions, inducing conformational changes, between the complex components, overview ?
-
?
reduced ferredoxin + H+ + N2 + ATP + H2O Azotobacter vinelandii enzyme complex is responsible for the majority of biological nitrogen fixation oxidized ferredoxin + H2 + NH3 + ADP + phosphate
-
ir

Organism

Organism UniProt Comment Textmining
Azotobacter vinelandii P00459
-
-

Purification (Commentary)

Purification (Comment) Organism
mutant betaG69S Azotobacter vinelandii

Reaction

Reaction Comment Organism Reaction ID
4 reduced ferredoxin + 8 H+ + N2 + 16 ATP + 16 H2O = 4 oxidized ferredoxin + H2 + 2 NH3 + 16 ADP + 16 phosphate overall catalytic mechanism, overview, structures of active site metal clusters, interactions of substrate and active site, active site relevant residues are Arg96, Val70, Gly69, and His195, substrate binding mechanism of complex components, mechanism of MgATP hydrolysis and electron transfer, overview Azotobacter vinelandii

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
acetylene + ?
-
Azotobacter vinelandii ethylene + ?
-
?
CS2 + ? slow turnover Azotobacter vinelandii H2S + ?
-
?
cyanamide + ?
-
Azotobacter vinelandii ?
-
?
cyanide + ?
-
Azotobacter vinelandii ?
-
?
methyl isocyanide + ?
-
Azotobacter vinelandii ?
-
?
additional information the activity of the enzyme complex is regulated by specific interactions, inducing conformational changes, between the complex components, overview Azotobacter vinelandii ?
-
?
additional information catalytic role of the molybdenum-iron protein, with P-cluster, and the Fe protein Azotobacter vinelandii ?
-
?
N2H4 + ?
-
Azotobacter vinelandii ?
-
?
N2O + ?
-
Azotobacter vinelandii ?
-
?
N3- + ?
-
Azotobacter vinelandii ?
-
?
reduced ferredoxin + H+ + N2 + ATP + H2O enzyme complex is responsible for the majority of biological nitrogen fixation Azotobacter vinelandii oxidized ferredoxin + H2 + NH3 + ADP + phosphate
-
ir
reduced ferredoxin + H+ + N2 + ATP + H2O turnover cycle scheme, MgATP is required for activity, mechanism of MgATP hydrolysis and electron transfer with an important role of switch I and II within the Fe protein Azotobacter vinelandii oxidized ferredoxin + H2 + NH3 + ADP + phosphate
-
ir

Subunits

Subunits Comment Organism
More overall enzyme complex structure with the MoFe protein, containing FeMo-cofactors and P-clusters, and 2 iron proteins, one with a [4Fe4S] cluster and MgATP, overview, components are encoded by the nif genes Azotobacter vinelandii

Cofactor

Cofactor Comment Organism Structure
ATP 2 MgATP binding sites on the iron protein, binding changes the redox status of the [4Fe4S] cluster of the iron protein, mechanism, overview Azotobacter vinelandii
Ferredoxin
-
Azotobacter vinelandii