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Distinct forms of the haem o ‐Cu binuclear site of oxidised cytochrome bo from Escherichia coli
Author(s) -
Watmough Nicholas J.,
Cheesman Myles R.,
Gennis Robert B.,
Greenwood Colin,
Thomson Andrew J.
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)80056-z
Subject(s) - cytochrome , chemistry , electron paramagnetic resonance , formate , cytochrome b , carboxylate , stereochemistry , crystallography , cytochrome c peroxidase , photochemistry , biochemistry , nuclear magnetic resonance , enzyme , mitochondrial dna , gene , catalysis , physics
Oxidised, formate‐bound and fluoride‐bound forms of E. coli cytochrome bo give rise to an electronic absorption band near 630 nm, diagnostic of high‐spin ferrric haem o , whose position is sensitive to the nature of the bound anion. In all three forms, haem o remains spin‐coupled to cu B (II), resulting in distinct broad X‐band EPR signals. Those of formate‐bound cytochrome bo are similar to the signals seen in slow cytochrome aa 3 but cannot be induced by incubation at acid pH suggesting that the endogenous earboxylate believed to be important in slow cytochrome aa 3 is not present in cytochrome bo . The oxidised form gives rise to novel EPR signals at g = 3.74 and g = 3.08 which have not been detected in cytochrome aa 3 and may arise from a weak magnetic coupling between high‐spin haem o , S = 5/2, and Cu b (ii), S = ½.