Missense exonic mitochondrial mutation in cytochrome b gene of Saccharomyces cerevisiae, resulting in core protein deficiency in complex III of the respiratory chain

Abstract

The level of core protein I and subunit VI of mitochondrial complex III (which are coded by the nuclear genome) was found to be greatly diminished in a yeast strain carrying a mutation (W7) in the mitochondrial gene coding for cytochrome b. This suggests that intricate interactions occur in complex III biogenesis between proteins of cytoplasmic and mitochondrial origin. This mutant was characterized by a low cytochrome b level and a loss of activity in the b-c1 segment of the respiratory chain. It was compared to another mutant showing similar biochemical characteristics, but which had integrated core protein I, as shown by antibody binding experiments. In mutant devoid of core protein I, cytochrome b was found to be reducible by NADH but not by succinate, suggesting two different electron transfer pathways inside comples III from each substrate to cytochrome b heme(s).

Electron‐transfer restoration by vitamin K3 in a complex III‐deficient mutant of S. cerevisiae and sequence of the corresponding cytochrome b mutation

“…The non-respiratory growing W7 mutant has been shown previously to be strongly affected in the assembly of the bcl complex, as indicated by the loss of ability to bind the high-affinity inhibitor antimycin [16] and by the drastic reduction in several of the enzyme polypeptide subunits it con- tains; the spectral cytochrome b content of mutant W7 amounted to only 1507o of that of the wild type while those of cytochromes c and aa3 were 65 and 37070, respectively [2]. Activity measurements at the mitochondrial level revealed the nearly complete absence of QHz-cytochrome c reductase activity; succinate-Q, NADH-Q and cytochrome c oxidase activities were substantially reduced by about 83, 38 and 64070, respectively, vs the wild type (see table 1).…”

“…00145793/89/$3.50 © 1989 Federation of European Biochemical Societiesdescribed previously [2,7]. Complex I activities were determined spectrophotometrically as in [8].…”

“…Cultures, preparation of mitochondria, spectral analysis, protein, succinate dehydrogenase activity, cytochrome-c oxidase and CoQ2H2-cytochrome c reductase activities have been described previously [2,7]. Complex I activities were determined spectrophotometrically as in [8].…”

“…Numerous apocytochrome b mutants defective in the ubiquinol-cytochrome c reductase segment (complex III) of the mitochondrial respiratory chain have been isolated in thcyeast S. cerevisiae [1]. The mutant W7, some of the biochemical properties of which have been described previously [2], is particularly interesting in that it is characterized by a low cytochrome b level, a loss of activity in the b-c1 segment of the respiratory chain and a decrease in other complex III subunits coded for by the nuclear genome: core protein I, non-heme Fe-S and subunit VI. A similar phenotype has been described for the first time in a patient with mitochondrial myopathy [3]; the question as to whether the primary site of the mutation in this patient might be mitochondrial or nuclear has been discussed previously [4].…”

Mesenchymal Stem Cells: A Future Option for Intervening Disease Management

“…There are studies which indicate the dose dependency of the MSCs for successful regeneration, and we speculate that the ability of the MSCs to tolerate the stress at the pathological site is the mechanism behind the dose dependency [15,16]. However, another dimension of MSC's potential is in the therapeutic modulation of the given disease conditions or at least in animal models, through release of inducible factors without direct involvement of the MSCs by division or differentiation [17,18]. In such cases, the tissue revival post MSC treatment shows no trace of the transplanted cells by the common tracking methods like 5(6)-Carboxyfluorescein diacetate N-succinimidyl ester (CFSE) chase or Green Fluorescent Protein (GFP).…”