title: Functional alteration of cytochrome c oxidase by SURF1 mutations in Leigh syndrome.
abstract: Subacute necrotising encephalomyopathy (Leigh syndrome) due to cytochrome c oxidase (COX) deficiency is often caused by mutations in the SURF1 gene, encoding the Surf1 protein essential for COX assembly. We have investigated five patients with different SURF1 mutations resulting in the absence of Surf1 protein. All of them presented with severe and generalised COX defect. Immunoelectrophoretic analysis of cultured fibroblasts revealed 85% decrease of the normal-size COX complexes and significant accumulation of incomplete COX assemblies of 90-120 kDa. Spectrophotometric assay of COX activity showed a 70-90% decrease in lauryl maltoside (LM)-solubilised fibroblasts. In contrast, oxygen consumption analysis in whole cells revealed only a 13-31% decrease of COX activity, which was completely inhibited by detergent in patient cells but not in controls. In patient fibroblasts ADP-stimulated respiration was 50% decreased and cytofluorometry showed a significant decrease of mitochondrial membrane potential DeltaPsi(m) in state 4, as well as a 2.4-fold higher sensitivity of DeltaPsi(m) to uncoupler. We conclude that the absence of the Surf1 protein leads to the formation of incomplete COX complexes, which in situ maintain rather high electron-transport activity, while their H(+)-pumping is impaired. Enzyme inactivation by the detergent in patient cells indicates instability of incomplete COX assemblies.
authors.affiliation: Institute of Physiology and Centre for Integrated Genomics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Pecina
authors.forename: Markéta
authors.initials: M
authors.lastname: Capková
authors.forename: Subir K R
authors.initials: SK
authors.lastname: Chowdhury
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Drahota
authors.forename: Audrey
authors.initials: A
authors.lastname: Dubot
authors.forename: Alena
authors.initials: A
authors.lastname: Vojtísková
authors.forename: Hana
authors.initials: H
authors.lastname: Hansíková
authors.forename: Hana
authors.initials: H
authors.lastname: Houst'ková
authors.forename: Jirí
authors.initials: J
authors.lastname: Zeman
authors.forename: Catherine
authors.initials: C
authors.lastname: Godinot
authors.forename: Josef
authors.initials: J
authors.lastname: Houstek
mesh_terms: D004579:Electron Transport / Q000235:genetics / Q000502:physiology; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007888:Leigh Disease / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011506:Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011506:Proteins; C092928:Surf-1 protein; D003576:Electron Transport Complex IV