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Characterization of cytochrome b in the isolated ubiquinol‐cytochrome c 2 oxidoreductase from Rhodopseudomonas sphaeroides GA
Author(s) -
Gabellini Nadia,
Hauska Günter
Publication year - 1983
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(83)80136-7
Subject(s) - cytochrome , ubiquinol , cytochrome c1 , cytochrome b , chemistry , cytochrome c , coenzyme q – cytochrome c reductase , rhodobacter sphaeroides , cytochrome b6f complex , stereochemistry , photochemistry , photosynthetic reaction centre , crystallography , biochemistry , electron transfer , mitochondrion , photosynthesis , mitochondrial dna , gene , enzyme
Extinction coefficients for cytochrome b and c 1 in the isolated cytochrome bc 1 complex from Rhodopseudomonas sphaeroides GA have been determined. They are 25 mM −1 .cm −1 at 561 nm for cytochrome b and 17.4 mM −1 .cm −1 at 553 nM for cytochrome c 1 for the difference between the reduced and the oxidized state. Cytochrome b is present in two forms in the complex. One form has an E m7 of 50 mV, an α‐peak of 557 nm at liquid N 2 temperature and of 561 nm at RT, which is red‐shifted by antimycin A. The other form has an E m7 of −90 mV, a double α‐peak of 555 and 561 nm at liquid N 2 temperature corresponding to 559 and 566 nm at RT. The absorption at 566 nm is red‐shifted by myxothiazol. The two shifts are independent of each other. Both midpoint potentials of cytochromes b are pH‐dependent. The redox center compositions of the cytochrome bc 1 complexes from Rhodopseudomonas sphaeroides and from mitochondria are identical.