Mie Yasuhiro, Mizutani Fumio, Uno Tadayuki, Yamada Chiho, Nishiyama Katsuhiko, Taniguchi Isao
National Institute of Advanced Industrial Science and Technology, 2-17-2-1, Tsukisamu-higashi, Toyohira, Sapporo 062-8517, Japan.
J Inorg Biochem. 2005 May;99(5):1245-9. doi: 10.1016/j.jinorgbio.2005.03.001.
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.
在氧化铟电极上观察到了细胞色素b562快速且可逆的电子转移反应。在pH 6.5时，估计的异相电子转移速率常数（k0'）为k0'≥5.0×10⁻³ cm s⁻¹。当野生型细胞色素b562中作为轴向配体与血红素铁配位的甲硫氨酸-7（Met-7）残基被丙氨酸或甘氨酸残基取代时，一个与血红素铁结合的水分子出现，电子转移速率常数分别降至1.3×10⁻³和1.8×10⁻³ cm s⁻¹。电子转移速率的这种降低可能是由于氧化还原位点结构变化的重组能更大。用丙氨酸或甘氨酸取代Met-7后，细胞色素b562的中点电位负移了约135 mV。与天然肌红蛋白相比，突变分子的氰化物解离动力学相似。
