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Cytochrome bo from E. coli does not exhibit the same proton transfer characteristics as the bovine cytochrome c oxidase during oxygen reduction
Author(s) -
Hallén Stefan,
Svensson Margareta,
Nilsson Thomas
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)81093-f
Subject(s) - chemistry , cytochrome c oxidase , electron transfer , cytochrome , proton , oxygen , stoichiometry , kinetics , cytochrome c , oxidase test , electron transport chain , reaction rate constant , photochemistry , electron transport complex iv , proton coupled electron transfer , stereochemistry , enzyme , biochemistry , organic chemistry , mitochondrion , physics , quantum mechanics
The reaction where fully reduced cytochrome bo from E. coli partially reduces dioxygen has been characterized with respect to the kinetics of the associated proton uptake, and with respect to the pH‐ and D 2 O‐sensitivity of the electron transfer reactions. A monophasic proton uptake with a rate constant of about 8 × 10 3 s −1 and a stoichiometry of 0.8 H + / bo were recorded, using the indicator dye, Cresol red, at pH 8.2. The electron transfer reactions were independent of pH in the range 6.0–9.5 and were not affected by exchanging H 2 O toD 2 O as solvent. Comparison of these results with those obtained in an earlier investigation of the bovine cytochrome c oxidase [(1992) Biochemistry 31, 11853‐11859], indicates differences between the two oxidases with respect to the role of protons in oxygen reduction and/or the mechanism of proton uptake from the medium.