title: Efflux-mediated heavy metal resistance in prokaryotes.
abstract: What makes a heavy metal resistant bacterium heavy metal resistant? The mechanisms of action, physiological functions, and distribution of metal-exporting proteins are outlined, namely: CBA efflux pumps driven by proteins of the resistance-nodulation-cell division superfamily, P-type ATPases, cation diffusion facilitator and chromate proteins, NreB- and CnrT-like resistance factors. The complement of efflux systems of 63 sequenced prokaryotes was compared with that of the heavy metal resistant bacterium Ralstonia metallidurans. This comparison shows that heavy metal resistance is the result of multiple layers of resistance systems with overlapping substrate specificities, but unique functions. Some of these systems are widespread and serve in the basic defense of the cell against superfluous heavy metals, but some are highly specialized and occur only in a few bacteria. Possession of the latter systems makes a bacterium heavy metal resistant.
authors.affiliation: Institute of Microbiology, Molecular Microbiology, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 3, 06099 Halle/Saale, Germany. d.nies@mikrobiologie.uni-halle.de
authors.forename: Dietrich H
authors.initials: DH
authors.lastname: Nies
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000378:metabolism; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D004352:Drug Resistance, Microbial; D005798:Genes, Bacterial / Q000235:genetics; D017136:Ion Transport / Q000502:physiology; D019216:Metals, Heavy / Q000378:metabolism* / Q000494:pharmacology / Q000633:toxicity; D011387:Prokaryotic Cells / Q000187:drug effects / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D019216:Metals, Heavy; D000251:Adenosine Triphosphatases