Lookup NU author(s): Dr Anna Mitchell,
Dr Andrew Schaefer,
Dr Margaret Jackson,
Professor Doug Turnbull,
Professor Robert Taylor
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Whereas the majority of disease-related mitochondrial DNA mutations exhibit significant biochemical and clinical heterogeneity, mutations within the mitochondrially encoded human cytochrome b gene (MTCYB) are almost exclusively associated with isolated complex III deficiency in muscle and a clinical presentation involving exercise intolerance. Recent studies have shown that a small number of MTCYB mutations are associated with a combined enzyme complex defect involving both complexes I and III, on account of the fact that an absence of assembled complex III results in a dramatic loss of complex I, confirming a structural dependence between these two complexes. We present the biochemical and molecular genetic studies of a patient with both muscle and brain involvement and a severe reduction in the activities of both complexes I and III in skeletal muscle due to a novel mutation in the MTCYB gene that predicts the substitution (Arg318Pro) of a highly conserved amino acid. Consistent with the dramatic biochemical defect, Western blotting and BN-PAGE experiments demonstrated loss of assembled complex I and III subunits. Biochemical studies of the equivalent amino-acid substitution (Lys319Pro) in the yeast enzyme showed a loss of enzyme activity and decrease in the steady-state level of bc1 complex in the mutant confirming pathogenicity. © 2005 FEBS.
Author(s): Blakely EL, Mitchell AL, Fisher N, Meunier B, Nijtmans LG, Schaefer AM, Jackson MJ, Turnbull DM, Taylor RW
Publication type: Article
Publication status: Published
Journal: FEBS Journal
ISSN (print): 17424-64X
ISSN (electronic): 1742-4658
Publisher: Wiley-Blackwell Publishing Ltd.
PubMed id: 16008558
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