Direct electrochemistry of engineered cytochrome b562 molecules with a ligand binding pocket.
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.
Mie
Yasuhiro
Y
National Institute of Advanced Industrial Science and Technology, 2-17-2-1, Tsukisamu-higashi, Toyohira, Sapporo 062-8517, Japan. yasuhiro.mie@aist.go.jp
Mizutani
Fumio
F
Uno
Tadayuki
T
Yamada
Chiho
C
Nishiyama
Katsuhiko
K
Taniguchi
Isao
I
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
D003573:Cytochrome b Group; D029968:Escherichia coli Proteins; D008024:Ligands; D011994:Recombinant Proteins; C017850:cytochrome b562, E coli