title: Human disease-related mutations in cytochrome b studied in yeast.
abstract: Several mutations in the mitochondrially encoded cytochrome b have been reported in patients. To characterize their effect, we introduced six "human" mutations, namely G33S, S152P, G252D, Y279C, G291D, and Delta252-259 in the highly similar yeast cytochrome b. G252D showed wild type behavior in standard conditions. However, Asp-252 may interfere with structural lipid and, in consequence, destabilize the enzyme assembly, which could explain the pathogenicity of the mutation. The mutations G33S, S152P, G291D, and Delta252-259 were clearly pathogenic. They caused a severe decrease of the respiratory function and altered the assembly of the iron-sulfur protein in the bc(1) complex, as observed by immunodetection. Suppressor mutations that partially restored the respiratory function impaired by S152P or G291D were found in or close to the hinge region of the iron-sulfur protein, suggesting that this region may play a role in the stable binding of the subunit to the bc(1) complex. Y279C caused a significant decrease of the bc(1) function and perturbed the quinol binding. The EPR spectra showed an altered signal, indicative of a lower occupancy of the Q(o) site. The effect of human mutation of residue 279 was confirmed by another change, Y279A, which had a more severe effect on Q(o) site properties. Thus by using yeast as a model system, we identified the molecular basis of the respiratory defect caused by the disease mutations in cytochrome b.
authors.affiliation: Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Fisher
authors.forename: C Kate
authors.initials: CK
authors.lastname: Castleden
authors.forename: Ingrid
authors.initials: I
authors.lastname: Bourges
authors.forename: Gael
authors.initials: G
authors.lastname: Brasseur
authors.forename: Genevieve
authors.initials: G
authors.lastname: Dujardin
authors.forename: Brigitte
authors.initials: B
authors.lastname: Meunier
mesh_terms: D001224:Aspartic Acid / Q000737:chemistry; D001665:Binding Sites; D015153:Blotting, Western; D045303:Cytochromes b / Q000737:chemistry / Q000235:genetics*; D045304:Cytochromes c / Q000378:metabolism; D003575:Cytochromes c1 / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D014450:Electron Transport Complex III / Q000737:chemistry; D005656:Fungal Proteins / Q000737:chemistry; D030342:Genetic Diseases, Inborn / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D007425:Intracellular Membranes / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D007700:Kinetics; D008055:Lipids / Q000737:chemistry; D008280:Magnetics; D008928:Mitochondria / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry; D013053:Spectrophotometry; D013489:Suppression, Genetic; D013696:Temperature; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D005656:Fungal Proteins; D007506:Iron-Sulfur Proteins; D008055:Lipids; D029701:Saccharomyces cerevisiae Proteins; D014451:Ubiquinone; D001224:Aspartic Acid; C060262:2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone; D045304:Cytochromes c; D045303:Cytochromes b; D003575:Cytochromes c1; C436959:Qcr7 protein, S cerevisiae; D014450:Electron Transport Complex III