title: Escherichia coli TehB requires S-adenosylmethionine as a cofactor to mediate tellurite resistance.
abstract: The Escherichia coli chromosomal determinant for tellurite resistance consists of two genes (tehA and tehB) which, when expressed on a multicopy plasmid, confer resistance to K(2)TeO(3) at 128 microg/ml, compared to the MIC of 2 microg/ml for the wild type. TehB is a cytoplasmic protein which possesses three conserved motifs (I, II, and III) found in S-adenosyl-L-methionine (SAM)-dependent non-nucleic acid methyltransferases. Replacement of the conserved aspartate residue in motif I by asparagine or alanine, or of the conserved phenylalanine in motif II by tyrosine or alanine, decreased resistance to background levels. Our results are consistent with motifs I and II in TehB being involved in SAM binding. Additionally, conformational changes in TehB are observed upon binding of both tellurite and SAM. The hydrodynamic radius of TehB measured by dynamic light scattering showed a approximately 20% decrease upon binding of both tellurite and SAM. These data suggest that TehB utilizes a methyltransferase activity in the detoxification of tellurite.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Liu
authors.forename: R J
authors.initials: RJ
authors.lastname: Turner
authors.forename: T L
authors.initials: TL
authors.lastname: Winstone
authors.forename: A
authors.initials: A
authors.lastname: Saetre
authors.forename: M
authors.initials: M
authors.lastname: Dyllick-Brenzinger
authors.forename: G
authors.initials: G
authors.lastname: Jickling
authors.forename: L W
authors.initials: LW
authors.lastname: Tari
authors.forename: J H
authors.initials: JH
authors.lastname: Weiner
authors.forename: D E
authors.initials: DE
authors.lastname: Taylor
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D012436:S-Adenosylmethionine / Q000378:metabolism*; D016415:Sequence Alignment; D013691:Tellurium / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C119920:tellurite resistance protein B, E coli; D012436:S-Adenosylmethionine; C026660:tellurous acid; D013691:Tellurium