1.12.99.6 CN- contains two CN- molecules at the active site 684608 1.12.99.6 CN- the auxiliary proteins HoxL and HoxV assist in assembly of the Fe(CN-)2CO moiety 704518 1.12.99.6 CN- the catalytic center is equipped with 1.8 CN- per protein molecule 704489 1.12.99.6 CO the auxiliary proteins HoxL and HoxV assist in assembly of the Fe(CN-)2CO moiety 704518 1.12.99.6 CO the catalytic center is equipped with one CO 704489 1.12.99.6 Fe - 439638 1.12.99.6 Fe 0.134 mmol Fe per g protein 659878 1.12.99.6 Fe 10.6 atoms per mol enzyme 439639 1.12.99.6 Fe 10.9 mol per tetramer, 3Fe-4S cluster 439640 1.12.99.6 Fe 11 atoms per mol enzyme 439634 1.12.99.6 Fe 11.3 mol per mol of enzyme 439643 1.12.99.6 Fe 12.2 mol per mol enzyme, iron-sulfur protein 439648 1.12.99.6 Fe 14 atoms per molecule, 2 4Fe-4S clusters 439642 1.12.99.6 Fe 21 atoms per mol enzyme, 5 4Fe-4S cluster and 1 2Fe-2S cluster 439641 1.12.99.6 Fe 31 g iron per 185 g enzyme 439632 1.12.99.6 Fe 3Fe-xS and 4Fe-4S clusters 439636 1.12.99.6 Fe 4Fe-4S and 2Fe-2S clusters 439647 1.12.99.6 Fe 4Fe-4S cluster 439631 1.12.99.6 Fe 4Fe-4S clusters 439644 1.12.99.6 Fe 7-8 atoms per mol enzyme, 3Fe-4S cluster 439635 1.12.99.6 Fe 7.3 mol per enzyme 439649 1.12.99.6 Fe contains bimetallic center in active site 658082 1.12.99.6 Fe contains Fe-s clusters 658082 1.12.99.6 Fe contains FeNi-center 659310 1.12.99.6 Fe contains Ni-Fe bimetallic center as active site 659520 1.12.99.6 Fe contains several [4Fe-4S] clusters 657622 1.12.99.6 Fe contains several [4Fe-S] and [2Fe-2S] cluster 659523 1.12.99.6 Fe enzyme contains Ni-Fe center and Fe-S clusters 658972 1.12.99.6 Fe Fe-hydrogenase 657778 1.12.99.6 Fe FeFe-hydrogenase 671932 1.12.99.6 Fe FeNi-hydrogenase 659355 1.12.99.6 Fe has Fe-S clusters, contains 10 g atoms of Fe per mol of protein 688848 1.12.99.6 Fe HydADELTAEFG binds a [4Fe-4S] cluster 702323 1.12.99.6 Fe hydrogen bonding affects the [NiFe] active site 675615 1.12.99.6 Fe iron azadithiolate phosphine-substituted complex and its protonated species featuring the NH proton and/or bridging Fe hydride, [Fe2(micro-S(CH2)2NnPr(H)m(CH2)2S)(micro-H)n(CO)4(PMe3)2]2 (2m+2n)+, mimic the active site of Fe-only hydrogenase. The ability to accept protons for the aza nitrogen and the Fe sites is essential for the enzymatic H2 production at the mild potential 704016 1.12.99.6 Fe iron center octahedrally coordinated by one dithiothreitol-sulfur and one dithiothreitol-oxygen, two CO, the nitrogen of 2-pyridinol and the 6-formylmethyl group of 2-pyridinol in an acyliron ligation 703728 1.12.99.6 Fe iron-sulfur cluster as well as 4Fe-4S-ferredoxin-type cluster 439627, 439628 1.12.99.6 Fe is composed of a small subunit, capable in coordinating one [3Fe4S] and two [4Fe4S] clusters 704489 1.12.99.6 Fe lacks the ferredoxin-like clusters, but contains the H-cluster [Fe4S4] component 703727 1.12.99.6 Fe membrane-bound [NiFe]-hydrogenase exhibits prominent electron paramagnetic resonance signals originating from [3Fe–4S]1 and [4Fe–4S]1 clusters 703746 1.12.99.6 Fe Ni-Fe active site. Presence of eight Fe-S clusters, three [2Fe-2S] clusters and five [4Fe-4S] clusters 674938 1.12.99.6 Fe NiFe-hydrogenase 657739, 658987 1.12.99.6 Fe protonation can take place in a terminal fashion at a single Fe or by bridging between two iron centres, protonation of a model of the subsite of [FeFe]-hydrogenase, [Fe2(m-pdt)(CO)4(PMe3)2], occurs via a two-step mechanism 703182 1.12.99.6 Fe protonation of diiron dithiolato complexes can occur at a single Fe site, even for symmetrical (FeI)2 compounds. The terminal hydride [HFe2(S2C3H6)(CO)2(dppv)2]+ catalyzes proton reduction at potentials 200 mV milder than the isomeric bridging hydride, thereby establishing a thermodynamic advantage for catalysis operating via terminal hydride 704012 1.12.99.6 Fe specific protein-protein interactions of maturation proteins may be required during [FeFe] cluster synthesis and/or insertion. Maturation proteins HydE and HydG interact with the [FeFe] hydrogenase large subunit HydA, which binds the H-cluster. Neither HydE nor HydG interact with the [FeFe] hydrogenase small subunit, HydB. No interaction of HydF, which catalyzes an energy-dependent step during H-cluster assembly or insertion, with either HydA or HydB 702813 1.12.99.6 Fe the auxiliary proteins HoxL and HoxV assist in assembly of the Fe(CN-)2CO moiety 704518 1.12.99.6 Fe the electron acceptor interacts only with the [FeS]distal cluster in the hydrogenase, and accordingly the autocatalyst is a hydrogenase form in which the [FeS]distal cluster holds an electron (i.e., at least the [FeS]distal cluster is reduced) 702707 1.12.99.6 Fe the Fe(CO)2(Pi-Pr3) site is rotated in solution, driven by steric factors. Fe atom featuring a vacant apical coordination position is an electrophilic Fe(I) center. One-electron oxidation of [Fe2(S2C2H4)(CN)(CO)3(dppv)]- results in 2e oxidation of 0.5 equiv to give the micro-cyano derivative [FeI2(S2C2H4)(CO)3(dppv)](micro-CN)[FeII2(S2C2H4)(micro-CO)(CO)2(CN)(dppv)] 704014 1.12.99.6 Fe the Hred form is assigned as a mixture of an Fe(I)Fe(I) form with an open site on the distal iron center and either a Fe(I)Fe(I) form in which the distal cyanide is protonated or a Fe(II)Fe(II) form with a bridging hydride ligand. The Hox form is assigned as a valence-localized Fe(I)Fe(II) redox level with an open site at the distal iron. The Hox air form is assigned as an Fe(II)Fe(II) redox level with OH- or OOH- bound to the distal iron center that may or may not have an oxygen atom bound to one of the sulfur atoms of the dithiolate linker 704013 1.12.99.6 Fe the HydA1 H-cluster consists of a [4Fe4S] cluster and a diiron site, 2FeH 702307 1.12.99.6 Fe the large subunit HoxC is purified without its small subunit. Two forms of HoxC are identified. Both forms contain iron but only substoichiometric amounts of nickel. One form is a homodimer of HoxC whereas the second also contains the Ni–Fe site maturation proteins HypC and HypB. Despite the presence of the Ni–Fe active site in some of the proteins, both forms, which lack the Fe–S clusters normally present in hydrogenases, cannot activate hydrogen. The incomplete insertion of nickel into the Ni–Fe site provides direct evidence that Fe precedes Ni in the course of metal center assembly 673617 1.12.99.6 Fe two ferredoxin-like [Fe4S4] clusters 703727 1.12.99.6 Fe uptake [NiFe] hydrogenase 674936 1.12.99.6 Fe [FeFe]-hydrogenase.The H cluster (hydrogen-activating cluster) contains a di-iron centre ([2Fe]H subcluster, a (L)(CO)(CN)Fe(mu-RS2)(mu-CO)Fe (CysS)(CO)(CN) group) covalently attached to a cubane iron-sulphur cluster ([4Fe-4S]H subcluster). The added redox equivalent not only affects the [4Fe-4S]H subcluster, but also the di-iron centre 674923 1.12.99.6 Fe [FeS] cluster 703727 1.12.99.6 Fe [NiFeSe]-hydrogenase, absence of a [3Fe-4S] cluster 704162 1.12.99.6 Fe [NiFe] hydrogenase 677151 1.12.99.6 Fe2+ 1 mM increases hydrogenase activity 4fold, is not sufficient to increase hydrogenase activities without S-adenosyl methionine and the standard 20 L-amino acids 706442 1.12.99.6 Fe2+ contains a Fe2+-binding site 684648 1.12.99.6 Fe2+ essential element for the assembly and maturation, the addition of Fe-EDTA (0.05 mM) does not affect the level of hydrogenase activity 710951 1.12.99.6 Fe2+ the active site has a characteristic bis(micro-thiolato)NiFe unit, where the Ni atom and the Fe atom are bridged by an undetermined oxygen-bearing ligand. This ligand probably derives from the aqueous solvent and is therefore most likely to be H2O, OH- or O2-. A NiFe complex is not able to activate H2 when coordinated with an CH3CN ligand, thus a highly labile ligand that is simultaneously able to act as a Lewis base for the heterolytic activation of H2 is crucial to the action of H2ase. The CH3CN-coordinated Ni(II)Fe(II) complex is unstable in the presence of water and decomposed to the Ni(II) complex and the Fe(II) complex via the Fe-S bond cleavage in water. In order to synthesise H2O-coordinated NiFe complexes in aqueous media, the Lewis acidity of the Fe centre must be increased to form strong Fe-S bonds. Thus, organometallic ligands with a back-donating character to form Fe-C bonds are required 703360 1.12.99.6 Iron contains 0.23 Fe atoms per molecule of large subunit HyhL 724185 1.12.99.6 Iron the enzyme harbors an iron-containing cofactor, in which a lowspin iron is complexed by a pyridone, two CO and a cysteine sulfur, [Fe] hydrogenase apoenzyme is converted completely into [Fe] hydrogenase holoenzyme by mixing the apoenzyme with a 3fold excess of the iron-containing [Fe] hydrogenase cofactor 687827 1.12.99.6 Iron within the catalytic centre one carbonyl and two cyanide ligands are covalently attached to the iron 686733 1.12.99.6 Mo 0.0025 mmol Mo per g protein 659878 1.12.99.6 additional information no increase in the hydrogenase activity is observed in response to ferric sulfate, ferric citrate, ferric ammonium citrate, and ferric nitrate 710951 1.12.99.6 Ni - 439638, 439647 1.12.99.6 Ni 0.0025 mmol Ni per g protein 659878 1.12.99.6 Ni 0.6-0.7 atoms per mol enzyme 439635 1.12.99.6 Ni 0.725 mol per enzyme 439649 1.12.99.6 Ni 0.9 atoms per mol enzyme 439634, 439639, 439641 1.12.99.6 Ni 0.9 mol per mol of enzyme 439643 1.12.99.6 Ni 1.06 mol per tetramer 439640 1.12.99.6 Ni 31 g nickel per 185 g enzyme 439632 1.12.99.6 Ni contains 1 g of atom of Ni per mol of protein 688848 1.12.99.6 Ni contains bimetallic center in active site 658082 1.12.99.6 Ni contains FeNi-center 659310 1.12.99.6 Ni contains Ni in the catalytic center 657622 1.12.99.6 Ni contains Ni-Fe bimetallic center as active site 659520 1.12.99.6 Ni enzyme contains Ni-Fe center 658972 1.12.99.6 Ni FeNi-hydrogenase 659355 1.12.99.6 Ni hydrogen bonding affects the [NiFe] active site 675615 1.12.99.6 Ni Ni-Fe active site 674938 1.12.99.6 Ni NiFe-hydrogenase 439629, 439630, 439631, 658082, 658987 1.12.99.6 Ni NiFe-hyrogenase 657739 1.12.99.6 Ni Rhizobium leguminosarum biovar viciae symbiotic hydrogenase activity and processing are limited by the level of nickel in agricultural soils 671433 1.12.99.6 Ni uptake [NiFe] hydrogenase 674936 1.12.99.6 Ni [NiFe] hydrogenase has two different oxidized states, Ni-A (unready, exhibits a lag phase in reductive activation) and Ni-B (ready). Ni-B possesses a monatomic nonprotein bridging ligand at the Ni-Fe active site, whereas Ni-A has a diatomic species 677151 1.12.99.6 Ni2+ - 702254 1.12.99.6 Ni2+ accessory protein HypB is necessary for Ni(II) incorporation into the hydrogenase protein. HypB has two metal-binding sites, a high-affinity Ni(II) site that includes ligands from the N-terminal domain and a low-affinity metal site located within the C-terminal GTPase domain 702218 1.12.99.6 Ni2+ contains a Ni2+-binding site 684648 1.12.99.6 Ni2+ essential element for the assembly and maturation, addition of 0.1 mM Ni2+ to the growth medium significantly enhances the hydrogenase activity. Nickel-treatment affects the level of the protein, but not the mRNA 710951 1.12.99.6 Ni2+ is composed of a large subunit, harboring the [NiFe] active site 704489 1.12.99.6 Ni2+ Ni-Fe active site assembly, nickel is absent in samples of HoxV 704518 1.12.99.6 Ni2+ the active site has a characteristic bis(micro-thiolato)NiFe unit, where the Ni atom and the Fe atom are bridged by an undetermined oxygen-bearing ligand. This ligand probably derives from the aqueous solvent and is therefore most likely to be H2O, OH- or O2-. A NiFe or NiRu complex are not able to activate H2 when coordinated with an CH3CN ligand, thus a highly labile ligand that is simultaneously able to act as a Lewis base for the heterolytic activation of H2 is crucial to the action of H2ase. The CH3CN-coordinated Ni(II)Fe(II) complex is unstable in the presence of water and decomposed to the Ni(II) complex and the Fe(II) complex via the Fe-S bond cleavage in water. In order to synthesise H2O-coordinated NiFe complexes in aqueous media, the Lewis acidity of the Fe centre must be increased to form strong Fe-S bonds. Thus, organometallic ligands with a back-donating character to form Fe-C bonds are required 703360 1.12.99.6 Ni2+ [NiFeSe]-hydrogenase 704162 1.12.99.6 selenium [NiFeSe]-hydrogenase 704162 1.12.99.6 Sulfide 10 atoms labile sulfide per mol enzyme 439634 1.12.99.6 Sulfide 10.8 mol acid labile sulfur per mol of enzyme 439643 1.12.99.6 Sulfide 12 atoms acid labile sulfur atoms per mol enzyme 439639 1.12.99.6 Sulfide 14.4 atoms per molecule 439642 1.12.99.6 Sulfide 24 g acid labile sulfide per 185 g enzyme 439632 1.12.99.6 Sulfide 7.2 mol labile sulfide per enzyme 439649 1.12.99.6 Sulfide 9.1 mol per mol enzyme, iron-sulfur protein 439648