Electron transfer processes in subunit I mutants of cytochrome bo quinol oxidase in Escherichia coli.
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.
Kobayashi
Kazuo
K
Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan.
Tagawa
Seiichi
S
Mogi
Tatsushi
T
D000595:Amino Acid Sequence; D017124:Conserved Sequence; D055590:Electromagnetic Phenomena; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D006418:Heme / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011199:Potentiometry; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011522:Protons; D011675:Pulse Radiolysis
D007473:Ion Channels; D050505:Mutant Proteins; D021122:Protein Subunits; D011522:Protons; D006418:Heme; C038862:cytochrome o oxidase; D003576:Electron Transport Complex IV