title: Control of the transition between Ni-C and Ni-SI(a) states by the redox state of the proximal Fe-S cluster in the catalytic cycle of [NiFe] hydrogenase.
abstract: [NiFe] hydrogenase catalyzes the reversible cleavage of H2. The electrons produced by the H2 cleavage pass through three Fe-S clusters in [NiFe] hydrogenase to its redox partner. It has been reported that the Ni-SI(a), Ni-C, and Ni-R states of [NiFe] hydrogenase are involved in the catalytic cycle, although the mechanism and regulation of the transition between the Ni-C and Ni-SI(a) states remain unrevealed. In this study, the FT-IR spectra under light irradiation at 138-198 K show that the Ni-L state of [NiFe] hydrogenase is an intermediate between the transition of the Ni-C and Ni-SI(a) states. The transition of the Ni-C state to the Ni-SI(a) state occurred when the proximal [Fe4S4]p(2+/+) cluster was oxidized, but not when it was reduced. These results show that the catalytic cycle of [NiFe] hydrogenase is controlled by the redox state of its [Fe4S4]p(2+/+) cluster, which may function as a gate for the electron flow from the NiFe active site to the redox partner.
authors.affiliation: Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5, Takayama-cho, Ikoma-shi, Nara 630-0192 (Japan); CREST, JST Gobancho, Chiyoda-ku, Tokyo 102-0076 (Japan).
authors.forename: Hulin
authors.initials: H
authors.lastname: Tai
authors.forename: Koji
authors.initials: K
authors.lastname: Nishikawa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Suzuki
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Higuchi
authors.forename: Shun
authors.initials: S
authors.lastname: Hirota
mesh_terms: D002384:Catalysis; D006864:Hydrogenase / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D010084:Oxidation-Reduction
chemical_list: D007506:Iron-Sulfur Proteins; C043296:nickel-iron hydrogenase; D006864:Hydrogenase
keywords: EPR spectroscopy; IR spectroscopy; biocatalysis; hydrogenases; iron-sulfur clusters