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A pulsed EPR study of redox‐dependent hyperfine interactions for the nickel centre of Desulfovibrio gigas hydrogenase
Author(s) -
Chapman Alan,
Cammack Richard,
Hatchikian Claude E.,
McCracken John,
Peisach Jack
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)81001-9
Subject(s) - hydrogenase , nickel , electron paramagnetic resonance , hyperfine structure , redox , desulfovibrio , chemistry , photochemistry , desulfovibrio vulgaris , nuclear magnetic resonance , inorganic chemistry , biochemistry , atomic physics , physics , enzyme , bacteria , biology , organic chemistry , genetics , sulfate
The nickel centre of hydrogenase from Desulfovibrio gigas was studied by electron spin echo envelope modulation (ESEEM) spectroscopy in the oxidized, unready (Ni‐A) and H 2 ‐reduced active (Ni‐C) states, both in H 2 O and 2 H 2 O solution. Fourier transforms of the 3‐pulse ESEEM, taken at 8.7 GHz, for Ni‐A and Ni‐C in H 2 O contained similar peaks with narrow linewidths at frequencies of 0.4, 1.2 and 1.6 MHz, and a broader peak centred at 4.5 MHz. At 11.6 GHz, the low frequency components showed small field‐dependent shifts, while the high frequency component was shifted to 5.1 MHz. These results are consistent with the presence of 14 N, possibly from imidazole, coupled to the nickel centre. In 2 H 2 O, Ni‐A was shown to be inaccessible for exchange with solvent deuterons. In contrast, Ni‐C was accessible to solvent exchange, with a deuterium population being in close proximity to the metal ion. Thus, the nickel environment of the active protein is different from that in the oxidized or unready state. On illumination of Ni‐C, although EPR changes are seen, 14 N coupling remains, and for the 2 H 2 O sample, deuterium coupling is also retained.