Open AccessStudy of the Hansenula anomala yeast flavocytochrome‐ b 2 ‐cytochrome‐ c complex
Author(s) -
THOMAS MarieAntoinette,
GERVAIS Michel,
FAVAUDON Vincent,
VALAT Pierre
Publication year - 1983
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1983.tb07691.x
Subject(s) - tetramer , chemistry , cytochrome , cytochrome c , heme , hemeprotein , dimer , cytochrome c oxidase , stereochemistry , porphyrin , flavin group , crystallography , photochemistry , biochemistry , enzyme , organic chemistry , mitochondrion
The reversible association of the Zn 2+ ‐substituted Hansenula anomala cytochrome c dimer (Thomas et al., preceding paper in this issue) to flavocytochrome b 2 in oxidized or lactate‐reduced state has been investigated by fluorimetry. The same method has been used for the determination of Zn‐cytochrome c complexing to defined proteolytic fragments of flavocytochrome b 2 , either heme‐ b 2 ‐containing monomers or a flavin‐linked tetramer. All these fragments but the isolated cytochrome b 2 core showed binding stoichiometries, K d values and ionic strength dependences quite similar to those found for native flavocytochrome b 2 . These data allowed localization of the single high‐affinity binding site of cytochrome c on a particular globule in the dehydrogenase domain of the flavocytochrome b 2 protomers. Quenching of the Zn‐porphyrin c fluorescence in the various complexes occurred with only minor changes of the fluorescence lifetime and did not show any direct relationship to the presence or the redox state of the heme b 2 group.