title: Proteomic identification of the Cus system as a major determinant of constitutive Escherichia coli silver resistance of chromosomal origin.
abstract: Although silver is one of the most potent and rapidly acting toxic metals to bacteria, silver-resistant bacteria do exist with low incidence. A proteomic approach was employed to identify the silver resistance determinants of a silver-resistant Escherichia coli strain isolated from stepwise selection against increasing concentrations of silver (Li et al. J. Bacteriol 1997, 179, 6127-32). Two-dimensional gel electrophoresis and mass spectrometry analysis revealed that members of the CusCFBA copper/silver chemiosmotic efflux system were highly expressed in the silver-resistant strain but undetectable in the parental silver-sensitive strain. Disruption of the cus locus of the silver-resistant strain resulted in a decrease of the minimum inhibitory concentration of Ag (+) from more than 1 mM to 12 microM. These results suggest that the chromosomally encoded Cus system, which naturally controls the periplasmic copper concentrations, is selectable to confer a constitutive silver resistance phenotype.
authors.affiliation: The Open Laboratory of Chemical Biology of the Institute of Molecular Technology for Drug Discovery and Synthesis, Department of Chemistry, Department of Anatomy, and Department of Surgery, The University of Hong Kong, Pokfulam, Hong Kong, China.
authors.forename: Chun-Nam
authors.initials: CN
authors.lastname: Lok
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Ho
authors.forename: Rong
authors.initials: R
authors.lastname: Chen
authors.forename: Paul Kwong-Hang
authors.initials: PK
authors.lastname: Tam
authors.forename: Jen-Fu
authors.initials: JF
authors.lastname: Chiu
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Che
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000032:analysis / Q000378:metabolism; D027682:Cation Transport Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D019327:Copper Sulfate / Q000494:pharmacology; D000079922:Copper Transport Proteins; D024881:Drug Resistance, Bacterial; D015180:Electrophoresis, Gel, Two-Dimensional; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D009154:Mutation; D040901:Proteomics / Q000379:methods; D012834:Silver / Q000494:pharmacology*; D012835:Silver Nitrate / Q000494:pharmacology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D001425:Bacterial Outer Membrane Proteins; D027682:Cation Transport Proteins; D000079922:Copper Transport Proteins; C506213:CusF protein, E coli; D029968:Escherichia coli Proteins; C078167:OMPA outer membrane proteins; D012834:Silver; D012835:Silver Nitrate; D019327:Copper Sulfate