Open AccessNMR studies of electron transfer mechanisms in a protein with interacting redox centres: Desulfovibrio gigas cytochrome c 3
Author(s) -
SANTOS Helena,
MOURA José J. G.,
MOURA Isabel,
LeGALL Jean,
XAVIER Antonio V.
Publication year - 1984
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1984.tb08190.x
Subject(s) - redox , chemistry , electron transfer , proton nmr , desulfovibrio , intramolecular force , heme , redox titration , cytochrome , hemeprotein , crystallography , stereochemistry , inorganic chemistry , photochemistry , biochemistry , organic chemistry , sulfate , enzyme
The proton NMR spectra of the tetrahaem cytochrome c 3 from Desulfovibrio gigas were examined while varying the pH and the redox potential. The analysis of the NMR reoxidation pattern was based on a model for the electron distribution between the four haems that takes into account haem‐haem redox interactions. The intramolecular electron exchange is fast on the NMR time scale (larger than 10 5 s −1 ). The NMR data concerning the pH dependence of the chemical shift of haem methyl resonances in different oxidation steps and resonance intensities are not compatible with a non‐interacting model and can be explained assuming a redox interaction between the haems. A complete analysis at pH*= 7.2 and 9.6, shows that the haem‐haem interacting potentials cover a range from ‐50mV to +60 mV. The midpoint redox potentials of some of the haems, as well as some of their interacting potentials, are pH‐dependent. The physiological relevance of the modulation of the haem midpoint redox potentials by both the pH and the redox potential of the solution is discussed.