title: Multiple roles for the twin arginine leader sequence of dimethyl sulfoxide reductase of Escherichia coli.
abstract: Dimethyl sulfoxide (Me(2)SO) reductase of Escherichia coli is a terminal electron transport chain enzyme that is expressed under anaerobic growth conditions and is required for anaerobic growth with Me(2)SO as the terminal electron acceptor. The trimeric enzyme is composed of a membrane extrinsic catalytic dimer (DmsAB) and a membrane intrinsic anchor (DmsC). The amino terminus of DmsA has a leader sequence with a twin arginine motif that targets DmsAB to the membrane via a novel Sec-independent mechanism termed MTT for membrane targeting and translocation. We demonstrate that the Met-1 present upstream of the twin arginine motif serves as the correct translational start site. The leader is essential for the expression of DmsA, stability of the DmsAB dimer, and membrane targeting of the reductase holoenzyme. Mutation of arginine 17 to aspartate abolished membrane targeting. The reductase was labile in the leader sequence mutants. These mutants failed to support growth on glycerol-Me(2)SO minimal medium. Replacing the DmsA leader with the TorA leader of trimethylamine N-oxide reductase produced a membrane-bound DmsABC with greatly reduced enzyme activity and inefficient anaerobic respiration indicating that the twin arginine leaders may play specific roles in the assembly of redox enzymes.
authors.affiliation: Medical Research Council Group in Molecular Biology of Membrane Proteins, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Sambasivarao
authors.forename: R J
authors.initials: RJ
authors.lastname: Turner
authors.forename: J L
authors.initials: JL
authors.lastname: Simala-Grant
authors.forename: G
authors.initials: G
authors.lastname: Shaw
authors.forename: J
authors.initials: J
authors.lastname: Hu
authors.forename: J H
authors.initials: JH
authors.lastname: Weiner
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D007506:Iron-Sulfur Proteins; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D016415:Sequence Alignment; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D001120:Arginine; D010088:Oxidoreductases; C045664:dimethyl sulfoxide reductase