title: Differing ability to transport nonmetal substrates by two RND-type metal exporters.
abstract: The metal-exporting systems CusCFBA of Escherichia coli and GesABC of Salmonella are resistance-nodulation-division (RND)-type multiprotein systems responsible for detoxification during metal stress. In this study, the substrate range was determined for each metal transport system and possible amino acid residues important in substrate specificity were identified. The Ges system, previously identified as a gold-efflux system, conferred resistance to the greatest number and variety of organic chemicals including chloramphenicol, not recognized previously as a substrate. Phylogenetic analysis showed that GesB is most closely related to a class of RND transporters including MexF that have been shown to be responsible for exporting fluoroquinolones, chloramphenicol, and biocides. However, many of the closest homologs of GesABC appear to play a role in metal resistance judging from the genetic context. In contrast, CusCFBA belongs to a distinct family of RND-type monovalent metal-exporter systems containing a number of essential metal-binding methionines, resulting in a much narrower substrate range.
authors.affiliation: Department of Soil, Water, and Environmental Science, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Otakuye
authors.initials: O
authors.lastname: Conroy
authors.forename: Eun-Hae
authors.initials: EH
authors.lastname: Kim
authors.forename: Megan M
authors.initials: MM
authors.lastname: McEvoy
authors.forename: Christopher
authors.initials: C
authors.lastname: Rensing
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008670:Metals / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D009930:Organic Chemicals / Q000378:metabolism*; D010802:Phylogeny; D011485:Protein Binding; D012475:Salmonella / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D008670:Metals; D009930:Organic Chemicals