title: Direct electrochemistry of engineered cytochrome b562 molecules with a ligand binding pocket.
abstract: The rapid and reversible electron transfer reaction of cytochrome b562 was observed at an In2O3 electrode. The estimated heterogeneous electron transfer rate constant (k0') was k0' > or = 5.0 x 10(-3) cm s(-1) at pH 6.5. When the methionine-7 (Met-7) residue, which coordinates to the heme iron as an axial ligand, of the wild-type cytochrome b562 was replaced by an Ala or Gly residue, a water molecule bound to the heme iron and the electron transfer rate constants decreased to 1.3 x 10(-3) and 1.8 x 10(-3) cm s(-1), respectively. This decrease in the electron transfer rate would be due to the larger reorganization energy for the structural change at the redox site. The midpoint potential of cytochrome b562 was shifted negatively by approximately 135 mV by replacing Met-7 with Ala or Gly. Similar dissociation kinetics of cyanide for the mutated molecules as compared to native myoglobin was obtained.
authors.affiliation: National Institute of Advanced Industrial Science and Technology, 2-17-2-1, Tsukisamu-higashi, Toyohira, Sapporo 062-8517, Japan. yasuhiro.mie@aist.go.jp
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Mie
authors.forename: Fumio
authors.initials: F
authors.lastname: Mizutani
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Uno
authors.forename: Chiho
authors.initials: C
authors.lastname: Yamada
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Nishiyama
authors.forename: Isao
authors.initials: I
authors.lastname: Taniguchi
mesh_terms: D019943:Amino Acid Substitution; D003573:Cytochrome b Group / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004563:Electrochemistry; D004566:Electrodes; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008024:Ligands; D010084:Oxidation-Reduction; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D003573:Cytochrome b Group; D029968:Escherichia coli Proteins; D008024:Ligands; D011994:Recombinant Proteins; C017850:cytochrome b562, E coli