title: Definition of the nuclear encoded protein composition of bovine heart mitochondrial complex I. Identification of two new subunits.
abstract: Mitochondrial NADH:ubiquinone oxidoreductase (complex I) from bovine heart is a complicated multisubunit, membrane-bound assembly. Seven subunits are encoded by mitochondrial DNA, and the sequences of 36 nuclear encoded subunits have been described. The subunits of complex I and two subcomplexes (Ialpha and Ibeta) were resolved on one- and two-dimensional gels and by reverse-phase high performance liquid chromatography. Mass spectrometric analysis revealed two previously unknown subunits in complex I, named B14.7 and ESSS, one in each subcomplex. Coding sequences for each protein were identified in data bases and were confirmed by cDNA cloning and sequencing. Subunit B14.7 has an acetylated N terminus, no presequence, and contains four potential transmembrane helices. It is homologous to subunit 21.3b from complex I in Neurospora crassa and is related to Tim17, Tim22, and Tim23, which are involved in protein translocation across the inner membrane. Subunit ESSS has a cleaved mitochondrial import sequence and one potential transmembrane helix. A total of 45 different subunits of bovine complex I have now been characterized.
authors.affiliation: Medical Research Council Dunn Human Nutrition Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 2XY, United Kingdom.
authors.forename: Joe
authors.initials: J
authors.lastname: Carroll
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Shannon
authors.forename: Ian M
authors.initials: IM
authors.lastname: Fearnley
authors.forename: John E
authors.initials: JE
authors.lastname: Walker
authors.forename: Judy
authors.initials: J
authors.lastname: Hirst
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002467:Cell Nucleus / Q000235:genetics; D002851:Chromatography, High Pressure Liquid; D042967:Electron Transport Complex I; D013058:Mass Spectrometry; D008929:Mitochondria, Heart / Q000201:enzymology*; D008969:Molecular Sequence Data; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D009492:Neurospora crassa / Q000201:enzymology; D021122:Protein Subunits; D021381:Protein Transport; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D021122:Protein Subunits; D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I