title: Transmembrane topology of the NuoL, M and N subunits of NADH:quinone oxidoreductase and their homologues among membrane-bound hydrogenases and bona fide antiporters.
abstract: Nicotinamide adenine dinucleotide-reduced form (NADH):quinone oxidoreductase (respiratory Complex I), F420H2 oxidoreductase and complex, membrane-bound NiFe-hydrogenase contain protein subunits homologous to a certain type of bona fide antiporters. In Complex I, these polypeptides (NuoL/ND5, NuoM/ND4, NuoN/ND2) are most likely core components of the proton pumping mechanism, and it is thus important to learn more about their structure and function. In this work, we have determined the transmembrane topology of one such polypeptide, and built a 2D structural model of the protein valid for all the homologous polypeptides. The experimentally determined transmembrane topology was different from that predicted by majority vote hydrophobicity analyses of members of the superfamily. A detailed phylogenetic analysis of a large set of primary sequences shed light on the functional relatedness of these polypeptides.
authors.affiliation: Department of Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, Box 124, 22100, Lund, Sweden.
authors.forename: Cecilie
authors.initials: C
authors.lastname: Mathiesen
authors.forename: Cecilia
authors.initials: C
authors.lastname: Hägerhäll
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism; D019069:Cell Respiration / Q000502:physiology; D004579:Electron Transport; D042967:Electron Transport Complex I; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D005810:Multigene Family; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D010802:Phylogeny; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D009097:Multienzyme Complexes; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I