title: LHON/MELAS overlap mutation in ND1 subunit of mitochondrial complex I affects ubiquinone binding as revealed by modeling in Escherichia coli NDH-1.
abstract: Defects in complex I due to mutations in mitochondrial DNA are associated with clinical features ranging from single organ manifestation like Leber hereditary optic neuropathy (LHON) to multiorgan disorders like mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome. Specific mutations cause overlap syndromes combining several phenotypes, but the mechanisms of their biochemical effects are largely unknown. The m.3376G>A transition leading to p.E24K substitution in ND1 with LHON/MELAS phenotype was modeled here in a homologous position (NuoH-E36K) in the Escherichia coli enzyme and it almost totally abolished complex I activity. The more conservative mutation NuoH-E36Q resulted in higher apparent K(m) for ubiquinone and diminished inhibitor sensitivity. A NuoH homolog of the m.3865A>G transition, which has been found concomitantly in the overlap syndrome patient with the m.3376G>A, had only a minor effect. Consequences of a primary LHON-mutation m.3460G>A affecting the same extramembrane loop as the m.3376G>A substitution were also studied in the E. coli model and were found to be mild. The results indicate that the overlap syndrome-associated m.3376G>A transition in MTND1 is the pathogenic mutation and m.3865A>G transition has minor, if any, effect on presentation of the disease. The kinetic effects of the NuoH-E36Q mutation suggest its proximity to the putative ubiquinone binding domain in 49kD/PSST subunits. In all, m.3376G>A perturbs ubiquinone binding, a phenomenon found in LHON, and decreases the activity of fully assembled complex I as in MELAS.
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, University of Oulu, Finland.
authors.forename: Jukka
authors.initials: J
authors.lastname: Pätsi
authors.forename: Pilvi
authors.initials: P
authors.lastname: Maliniemi
authors.forename: Salla
authors.initials: S
authors.lastname: Pakanen
authors.forename: Reetta
authors.initials: R
authors.lastname: Hinttala
authors.forename: Johanna
authors.initials: J
authors.lastname: Uusimaa
authors.forename: Kari
authors.initials: K
authors.lastname: Majamaa
authors.forename: Thomas
authors.initials: T
authors.lastname: Nyström
authors.forename: Marko
authors.initials: M
authors.lastname: Kervinen
authors.forename: Ilmo E
authors.initials: IE
authors.lastname: Hassinen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D042967:Electron Transport Complex I / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D017241:MELAS Syndrome / Q000235:genetics*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000502:physiology; D009245:NADH Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D029242:Optic Atrophy, Hereditary, Leber / Q000235:genetics*; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014451:Ubiquinone / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C540656:NuoH protein, E coli; D021122:Protein Subunits; D014451:Ubiquinone; D009245:NADH Dehydrogenase; D042967:Electron Transport Complex I