RESONANCE RAMAN STUDIES OF IRON-ONLY HYDROGENASES

The nature of the iron-sulfur clusters in oxidized and reduced forms o f Fe-only hydrogenases from Desulfovibrio vulgaris, Thermotoga maritim a, and Clostridium pasteurianum has been investigated by resonance Ram an spectroscopy. The results indicate the presence of ferredoxin-like [4Fe-4S]2+,+ and [2Fe-2S]2+,+ clusters in both T. maritima hydrogenase and C. pasteurianum hydrogenase 1, but only [4Fe-4S]2+,+ clusters in D. vulgaris hydrogenase. This necessitates a reevaluation of the iron- sulfur cluster composition of C. pasteurianum hydrogenase I and indica tes that the resonance Raman bands in the oxidized hydrogenase that we re previously attributed to the hydrogen activating center [Macor, K. A., Czernuszewicz, R. S., Adams, M. W. W., & Spiro, T. G. (1987) J. Bi ol. Chem. 262,9945-9947] arise from an indigenous [2Fe-2S]2+ cluster. No resonance Raman bands that could be uniquely attributed to the oxid ized or reduced hydrogen activating center were observed. This suggest s that the hydrogen activating center is a novel Fe center that is unr elated to any known type of Fe-S cluster.