title: Structural studies of the carbon monoxide complex of [NiFe]hydrogenase from Desulfovibrio vulgaris Miyazaki F: suggestion for the initial activation site for dihydrogen.
abstract: The carbon monoxide complex of [NiFe]hydrogenase from Desulfovibrio vulgaris Miyazaki F has been characterized by X-ray crystallography and absorption and resonance Raman spectroscopy. Nine crystal structures of the [NiFe]hydrogenase in the CO-bound and CO-liberated forms were determined at 1.2-1.4 A resolution. The exogenously added CO was assigned to be bound to the Ni atom at the Ni-Fe active site. The CO was not replaced with H(2) in the dark at 100 K, but was liberated by illumination with a strong white light. The Ni-C distances and Ni-C-O angles were about 1.77 A and 160 degrees, respectively, except for one case (1.72 A and 135 degrees ), in which an additional electron density peak between the CO and Sgamma(Cys546) was recognized. Distinct changes were observed in the electron density distribution of the Ni and Sgamma(Cys546) atoms between the CO-bound and CO-liberated structures for all the crystals tested. The novel structural features found near the Ni and Sgamma(Cys546) atoms suggest that these two atoms at the Ni-Fe active site play a role during the initial H(2)-binding process. Anaerobic addition of CO to dithionite-reduced [NiFe]hydrogenase led to a new absorption band at about 470 nm ( approximately 3000 M(-1)cm(-1)). Resonance Raman spectra (excitation at 476.5 nm) of the CO complex revealed CO-isotope-sensitive bands at 375/393 and 430 cm(-1) (368 and 413 cm(-1) for (13)C(18)O). The frequencies and relative intensities of the CO-related Raman bands indicated that the exogenous CO is bound to the Ni atom with a bent Ni-C-O structure in solution, in agreement with the refined structure determined by X-ray crystallography.
authors.affiliation: Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Ogata
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Mizoguchi
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Mizuno
authors.forename: Kunio
authors.initials: K
authors.lastname: Miki
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Adachi
authors.forename: Noritake
authors.initials: N
authors.lastname: Yasuoka
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Yagi
authors.forename: Osamu
authors.initials: O
authors.lastname: Yamauchi
authors.forename: Shun
authors.initials: S
authors.lastname: Hirota
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Higuchi
mesh_terms: D001665:Binding Sites; D002248:Carbon Monoxide / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D016969:Desulfovibrio vulgaris / Q000201:enzymology*; D005583:Fourier Analysis; D006859:Hydrogen / Q000737:chemistry* / Q000378:metabolism; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman
chemical_list: D009532:Nickel; D002248:Carbon Monoxide; D006859:Hydrogen; C043296:nickel-iron hydrogenase; D006864:Hydrogenase