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Role of a bound ubiquinone on reactions of the Escherichia coli cytochrome bo with ubiquinol and dioxygen
Author(s) -
Mogi Tatsushi,
Sato-Watanabe Mariko,
Miyoshi Hideto,
Orii Yutaka
Publication year - 1999
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/s0014-5793(99)01007-8
Subject(s) - ubiquinol , chemistry , photochemistry , cytochrome , electron transfer , stereochemistry , cytochrome c1 , electron transport chain , coenzyme q – cytochrome c reductase , cytochrome c , biochemistry , enzyme , mitochondrion
To probe the functional role of a bound ubiquinone‐8 in cytochrome bo ‐type ubiquinol oxidase from Escherichia coli , we examined reactions with ubiquinol‐1 and dioxygen. Stopped‐flow studies showed that anaerobic reduction of the wild‐type and the bound ubiquinone‐free (ΔUbiA) enzymes with ubiquinol‐1 immediately takes place with four kinetic phases. Replacement of the bound ubiquinone with 2,6‐dibromo‐4‐cyanophenol (PC32) suppressed the anaerobic reduction of the hemes with ubiquinol‐1 by eliminating the fast phase. Flow‐flash studies in the reaction of the fully reduced enzyme with dioxygen showed that the heme b to heme o electron transfer occurs with a rate constant of ∼10 4 s −1 in all three preparations. These results support our previous proposal that the bound ubiquinone is involved in facile oxidation of substrates in subunit II and subsequent intramolecular electron transfer to low‐spin heme b in subunit I.