Electron transfer processes in subunit I mutants of cytochrome bo quinol oxidase in Escherichia coli.

Kazuo Kobayashi, Seiichi Tagawa, Tatsushi Mogi

Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan.

Bioscience, biotechnology, and biochemistry 2009 Jul

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Cytochrome bo is a terminal quinol oxidase in the aerobic respiratory chain of Escherichia coli. Subunit I binds all four redox centers, and electrons are transferred from quinols to high-spin heme o and Cu(B) through a bound uniquinone-8 and low-spin heme b. To explore the role of conserved charged amino acid residues, we examined the one-electron transfer processes in subunit I mutants. We found that all the mutants examined increased the electron transfer rate from the bound quinone to heme b more than 40-fold. Tyr288 and Lys362 are key residues in the K-channel for charge compensation of the heme o-Cu(B) binuclear center with protons. The Tyr288Phe and Lys362Gln mutants showed 100-fold decreases in heme b-to-heme o electron transfer, accompanied by large increases in the redox potential of heme o. Our results indicate that electromagnetic coupling of hemes is important for facilitated heme-heme electron transfer in cytochrome bo.

Citation

Kazuo Kobayashi, Seiichi Tagawa, Tatsushi Mogi. Electron transfer processes in subunit I mutants of cytochrome bo quinol oxidase in Escherichia coli. Bioscience, biotechnology, and biochemistry. 2009 Jul;73(7):1599-603