In:
FEBS Letters, Wiley, Vol. 457, No. 2 ( 1999-08-27), p. 223-226
Abstract:
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 ∼1×10 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.
Type of Medium:
Online Resource
ISSN:
0014-5793
,
1873-3468
DOI:
10.1016/S0014-5793(99)01047-9
Language:
English
Publisher:
Wiley
Publication Date:
1999
detail.hit.zdb_id:
1460391-3
SSG:
12
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