title: Electrochemical and Infrared Spectroscopic Studies Provide Insight into Reactions of the NiFe Regulatory Hydrogenase from Ralstonia eutropha with O2 and CO.
abstract: The regulatory hydrogenase (RH) from Ralstonia eutropha acts as the H2-sensing unit of a two-component system that regulates biosynthesis of the energy conserving hydrogenases of the organism according to the availability of H2. The H2 oxidation activity, which was so far determined in vitro with artificial electron acceptors, has been considered to be insensitive to O2 and CO. It is assumed that bulky isoleucine and phenylalanine amino acid residues close to the NiFe active site "gate" gas access, preventing molecules larger than H2 interacting with the active site. We have carried out sensitive electrochemical measurements to demonstrate that O2 is in fact an inhibitor of H2 oxidation by the RH, and that both H(+) reduction and H2 oxidation are inhibited by CO. Furthermore, we have demonstrated that the inhibitory effect of O2 arises due to interaction of O2 with the active site. Using protein film infrared electrochemistry (PFIRE) under H2 oxidation conditions, in conjunction with solution infrared measurements, we have identified previously unreported oxidized inactive and catalytically active reduced states of the RH active site. These findings suggest that the RH has a rich active site chemistry similar to that of other NiFe hydrogenases.
authors.affiliation: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford, OX1 3QR, U.K.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Ash
authors.affiliation: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford, OX1 3QR, U.K.
authors.forename: Juan
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford, OX1 3QR, U.K.
authors.forename: Nathan
authors.initials: N
authors.lastname: Coutard
authors.affiliation: Institut für Chemie, Technische Universität Berlin , PC14, Berlin, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Heidary
authors.affiliation: Institut für Chemie, Technische Universität Berlin , PC14, Berlin, Germany.
authors.forename: Marius
authors.initials: M
authors.lastname: Horch
authors.affiliation: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford, OX1 3QR, U.K.
authors.forename: Ingvild
authors.initials: I
authors.lastname: Gudim
authors.affiliation: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford, OX1 3QR, U.K.
authors.forename: Thomas
authors.initials: T
authors.lastname: Simler
authors.affiliation: Institut für Chemie, Technische Universität Berlin , PC14, Berlin, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Zebger
authors.affiliation: Institut für Chemie, Technische Universität Berlin , PC14, Berlin, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Lenz
authors.affiliation: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford, OX1 3QR, U.K.
authors.forename: Kylie A
authors.initials: KA
authors.lastname: Vincent
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry / Q000378:metabolism*; D020118:Cupriavidus necator / Q000201:enzymology*; D055664:Electrochemical Techniques; D006859:Hydrogen / Q000737:chemistry / Q000378:metabolism; D006864:Hydrogenase / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D013055:Spectrophotometry, Infrared
chemical_list: D002248:Carbon Monoxide; D006859:Hydrogen; C043296:nickel-iron hydrogenase; D006864:Hydrogenase; D010100:Oxygen