Effects of mutations in mitochondrial cytochrome b in yeast and man - Deficiency, compensation and disease

The mitochondrial cytochrome bc(1) complex is a key protonmotive component of eukaryotic respiratory chains. The mitochondrially encoded cytochrome b forms, with cytochrome c(1) and the iron-sulfur protein, the catalytic core of this multimeric enzyme. Mutations of cytochrome b have been reported in association with human diseases. In the highly homologous yeast cytochrome b, several mutations that impair the respiratory function, and reversions that correct the defect, have been described. In this paper, we re-examine the mutations in the light of the atomic structure of the complex, and disc uss the possible effect, at enzyme level, of the human cytochrome b mutatio ns and the correcting effect of the reversions.