Redox process of iron-sulfur clusters of the soluble-domain of the membrane-bound hydrogenase from Desulfovibrio vulgaris Miyazaki F studied by resonance Raman spectroscopy

Resonance Raman spectra of the soluble-domain of a membrane-bound hydrogenase from Desulfovibrio vulgaris Miyazaki F were recorded in different oxidation states. In the oxidized state, the Raman band due to the totally symmetric stretching mode of the iron-sulfur cluster was observed at 341 cm-1, which was attributed to the 3Fe-4S cluster. In the hydrogen-reduced state, only a weak and broad band was observed in its vicinity. During the process of reoxidation, a Raman band assignable to the 4Fe-4S cluster was observed at 333 cm-1 in the first step. Then, the band at 341 cm-1 became stronger and eventually dominated the spectrum. Corresponding changes were observed in the visible absorption spectra of the same sample. It was concluded from these observations that this hydrogenase has both 3Fe-4S and 4Fe-4S clusters and takes on at least three oxidation states, namely, oxidized, intermediate, and hydrogen-reduced ones.