Orientation-selected ENDOR of the active center in Chromatium vinosum [NiFe] hydrogenase in the oxidized "ready" state.
Electron nuclear double resonance (ENDOR) was applied to study the active site of the oxidized "ready" state, Ni(r), in the [NiFe] hydrogenase of Chromatium vinosum. The magnetic field dependence of the EPR was used to select specific subsets of molecules contributing to the ENDOR response by stepping through the EPR envelope. Three hyperfine couplings could be clearly followed over the complete field range. Two protons, H1 and H2, display a very similar large isotropic coupling of 12.5 and 12.6 MHz, respectively. Their dipolar coupling is small (2.1 and 1.4 MHz, respectively). A third proton, H3, exhibits a small isotropic coupling of 0.5 MHz and a larger anisotropic contribution of 3.5 MHz. Based on a comparison with structural data obtained from X-ray crystallography of single crystals of hydrogenases from Desulfovibrio gigas and D. vulgaris and the known g-tensor orientation of Ni(r), an assignment of the 1H hyperfine couplings could be achieved. H1 and H2 were assigned to the beta-CH2 protons of the bridging cysteine Cys533 and H3 could belong to a beta-CH2 proton of Cys68 or to a protonated cysteine (-SH) of Cys68 or Cys530.
Gessner
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Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Germany.
Stein
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Albracht
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SP
Lubitz
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D020134:Catalytic Domain; D002844:Chromatium / Q000201:enzymology*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011522:Protons
D011522:Protons; C043296:nickel-iron hydrogenase; D006864:Hydrogenase