title: The Saccharomyces cerevisiae succinate-ubiquinone oxidoreductase. Identification of Sdh3p amino acid residues involved in ubiquinone binding.
abstract: Succinate dehydrogenase (SDH) participates in the mitochondrial electron transport chain by oxidizing succinate to fumarate and transferring the electrons to ubiquinone. In yeast, it is composed of a catalytic dimer, comprising the Sdh1p and Sdh2p subunits, and a membrane domain, comprising two smaller hydrophobic subunits, Sdh3p and Sdh4p, which anchor the enzyme to the mitochondrial inner membrane. To investigate the role of the Sdh3p anchor polypeptide in enzyme assembly and catalysis, we isolated and characterized seven mutations in the SDH3 gene. Two mutations are premature truncations of Sdh3p with losses of one or three transmembrane segments. The remaining five are missense mutations that are clustered between amino acids 103 and 117, which are proposed to be located in transmembrane segment II or the matrix-localized loop connecting segments II and III. Three mutations, F103V, H113Q, and W116R, strongly but specifically impair quinone reductase activities but have only minor effects on enzyme assembly. The clustering of the mutations strongly suggests that a ubiquinone-binding site is associated with this region of Sdh3p. In addition, the biphasic inhibition of quinone reductase activity by a dinitrophenol inhibitor supports the hypothesis that two distinct quinone-binding sites are present in the yeast SDH.
authors.affiliation: Medical Research Council of Canada Group in the Molecular Biology of Membranes, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
authors.forename: K S
authors.initials: KS
authors.lastname: Oyedotun
authors.forename: B D
authors.initials: BD
authors.lastname: Lemire
mesh_terms: D000595:Amino Acid Sequence; D016227:Benzoquinones / Q000378:metabolism; D001665:Binding Sites; D003573:Cytochrome b Group / Q000378:metabolism; D004795:Enzyme Stability; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism*; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013385:Succinate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D014451:Ubiquinone / Q000378:metabolism*
chemical_list: D016227:Benzoquinones; D003573:Cytochrome b Group; D014451:Ubiquinone; C004532:quinone; D013385:Succinate Dehydrogenase; D016660:NAD(P)H Dehydrogenase (Quinone)