title: Extensive defects of mitochondrial electron-transfer chain in muscular cytochrome c oxidase deficiency.
abstract: This study was undertaken to estimate the extent of molecular defects in the mitochondrial electron-transfer chain of a patient with mitochondrial myopathy. Biochemical and immunochemical studies were performed on the skeletal muscle mitochondria. Spectrophotometry and enzyme activity measurements localized a definite defect at the segment of cytochrome c oxidase (complex IV) of the electron-transfer chain. Immunoblotting and immunoprecipitation studies using the anti-complex IV antibody revealed that the contents of subunits 1, 4, 5, 6, and 7 of complex IV were markedly diminished and that subunit 2 was almost absent. Immunohistochemistry of the muscle tissue revealed a considerable accumulation of immunoreactive materials of complex IV in the ragged-red fibers. The immunoblots using the anti-NADH-ubiquinone oxidoreductase antibody demonstrated that the contents of NADH-ubiquinone oxidoreductase subunits were 47% of control and that the contents of three subunits were considerably decreased. The contents of ubiquinol-cytochrome c oxidoreductase subunits were also somewhat low (77% of control) and one of the minor contaminants detected in the control was completely absent. High-resolution one-dimensional sodium dodecyl sulfate-urea-gel electrophoresis disclosed that six additional unidentified polypeptides in the control were markedly diminished or completely missing. These results demonstrate that the molecular defects in the mitochondrial electron-transfer chain are more extensive than would be expected from either spectral analysis or enzyme activity measurements alone, and involve not only complex IV but also NADH-ubiquinone oxidoreductase and ubiquinol-cytochrome c oxidoreductase and several unidentified mitochondrial proteins.
authors.affiliation: Department of Biomedical Chemistry, Faculty of Medicine, University of Nagoya, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
authors.forename: S
authors.initials: S
authors.lastname: Miyabayashi
authors.forename: M
authors.initials: M
authors.lastname: Nishikimi
authors.forename: H
authors.initials: H
authors.lastname: Suzuki
authors.forename: Y
authors.initials: Y
authors.lastname: Shimomura
authors.forename: K
authors.initials: K
authors.lastname: Ito
authors.forename: K
authors.initials: K
authors.lastname: Narisawa
authors.forename: K
authors.initials: K
authors.lastname: Tada
authors.forename: T
authors.initials: T
authors.lastname: Ozawa
mesh_terms: D000328:Adult; D002648:Child; D030401:Cytochrome-c Oxidase Deficiency; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000172:deficiency; D004591:Electrophoresis, Polyacrylamide Gel; D006651:Histocytochemistry; D006801:Humans; D007124:Immunoenzyme Techniques; D007163:Immunosorbent Techniques; D008297:Male; D008931:Mitochondria, Muscle / Q000201:enzymology* / Q000473:pathology; D009132:Muscles / Q000201:enzymology* / Q000473:pathology; D009135:Muscular Diseases / Q000209:etiology* / Q000473:pathology; D016660:NAD(P)H Dehydrogenase (Quinone); D011808:Quinone Reductases / Q000172:deficiency
chemical_list: D016660:NAD(P)H Dehydrogenase (Quinone); D011808:Quinone Reductases; D014450:Electron Transport Complex III