Spectroscopic characterization of the nickel and iron-sulphur clusters of hydrogenase from the purple photosynthetic bacterium Thiocapsa roseopersicina. 2. Electron spin-echo spectroscopy.
Pulsed electron-spin-resonance techniques were applied to the hydrogenase of the purple photosynthetic bacterium Thiocapsa roseopersicina, an enzyme which contains nickel and iron-sulphur clusters but no flavin. The linear electric field effect profile of the spectrum in the region of g = 2.01 indicated that the strong ESR signal in the oxidized protein is due to a [3Fe-4S] cluster. The electron spin-echo envelope of this spectrum was modulated by hyperfine interactions with 1H and 14N nuclei, probably from the polypeptide chain. The ESR spectrum of this species shows a complex pattern arising from spin-spin interaction with another paramagnet. When the protein was partially reduced by ascorbate plus phenazine methosulphate, the complexity of the spectrum was abolished but the form of the electron spin-echo envelope modulation (ESEEM) pattern was unchanged. This indicates that the reversible disappearance of the spin-spin interaction pattern on partial reduction is not due to cluster interconversion to a [4Fe-4S] cluster. In the ESR spectrum of nickel(III), weak hyperfine interactions with 1H and 14N were also observed by ESEEM. The nature of the interacting nuclei is discussed.
Cammack
R
R
Department of Biochemistry, King's College, London, England.
Kovacs
K L
KL
McCracken
J
J
Peisach
J
J
D002841:Chromatiaceae / Q000201:enzymology*; D003080:Cold Temperature; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D006864:Hydrogenase / Q000032:analysis*; D007506:Iron-Sulfur Proteins / Q000032:analysis*; D008667:Metalloproteins / Q000032:analysis*; D009532:Nickel; D010084:Oxidation-Reduction
D007506:Iron-Sulfur Proteins; D008667:Metalloproteins; D009532:Nickel; C043296:nickel-iron hydrogenase; D006864:Hydrogenase