title: Electrostatic roles in electron transfer from [NiFe] hydrogenase to cytochrome c3from Desulfovibrio vulgaris Miyazaki F.
abstract: Electrostatic interactions between proteins are key factors that govern the association and reaction rate. We spectroscopically determine the second-order reaction rate constant (k) of electron transfer from [NiFe] hydrogenase (H2ase) to cytochrome (cyt) c3at various ionic strengths (I). The k value decreases with I. To analyze the results, we develop a semi-analytical formula for I dependence of k based on the assumptions that molecules are spherical and the reaction proceeds via a transition state. Fitting of the formula to the experimental data reveals that the interaction occurs in limited regions with opposite charges and with radii much smaller than those estimated from crystal structures. This suggests that local charges in H2ase and cyt c3play important roles in the reaction. Although the crystallographic data indicate a positive electrostatic potential over almost the entire surface of the proteins, there exists a small region with negative potential on H2ase at which the electron transfer from H2ase to cyt c3may occur. This local negative potential region is identical to the hypothetical interaction sphere predicted by the analysis. Furthermore, I dependence of k is predicted by the Adaptive Poisson-Boltzmann Solver considering all charges of the amino acids in the proteins and the configuration of H2ase/cyt c3complex. The calculation reproduces the experimental results except at extremely low I. These results indicate that the stabilization derived from the local electrostatic interaction in the H2ase/cyt c3complex overcomes the destabilization derived from the electrostatic repulsion of the overall positive charge of both proteins.
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Sugimoto
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kitazumi
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Shirai
authors.affiliation: Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Nishikawa
authors.affiliation: Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Higuchi
authors.affiliation: Department of Chemistry, Konan University, 8-9-1 Okamoto, Higashi-Nada, Kobe, Hyogo 658-8501, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan. Electronic address: kano.kenji.5z@kyoto-u.ac.jp.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kano
mesh_terms: D019069:Cell Respiration; D003574:Cytochrome c Group / Q000737:chemistry* / Q000378:metabolism; D016969:Desulfovibrio vulgaris / Q000201:enzymology*; D004579:Electron Transport; D004583:Electrons; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D011487:Protein Conformation; D060066:Protein Interaction Maps; D055672:Static Electricity
chemical_list: D003574:Cytochrome c Group; C017165:cytochrome c(3); C043296:nickel-iron hydrogenase; D006864:Hydrogenase
keywords: Cytochrome c(3); Electrostatic interaction; Hydrogenase; Local charge