The cobalt, zinc, and cadmium efflux system CzcABC from Alcaligenes eutrophus functions as a cation-proton antiporter in Escherichia coli.
AUTOR(ES)
Nies, D H
RESUMO
The function of the CzcABC protein complex, which mediates resistance to Co2+, Zn2+, and Cd2+ in Alcaligenes eutrophus by cation efflux, was investigated by using everted membrane vesicles of Escherichia coli and an acridine orange fluorescence quenching assay. Since metal cation uptake could not be measured with inside-out membrane vesicles prepared from A. eutrophus and since available E. coli strains did not express the Czc-mediated resistance to cobalt, zinc, and cadmium salts, mutants of E. coli which exhibited a Czc-dependent increase in heavy metal resistance were isolated. E. coli mutant strain EC351 constitutively accumulated Co2+, Zn2+, and Cd2+. In the presence of Czc, net uptake of these heavy metal cations was reduced to the wild-type level. Inside-out vesicles prepared from E. coli EC351 cells displayed a Czc-dependent uptake of Co2+, Zn2+, and Cd2+ and a cation-triggered acridine orange fluorescence increase. The czc-encoded protein complex CzcABC was shown to be a zinc-proton antiporter.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=176940Documentos Relacionados
- CzcR and CzcD, gene products affecting regulation of resistance to cobalt, zinc, and cadmium (czc system) in Alcaligenes eutrophus.
- New functions for the three subunits of the CzcCBA cation-proton antiporter.
- Plasmid-determined inducible efflux is responsible for resistance to cadmium, zinc, and cobalt in Alcaligenes eutrophus.
- Cloning of plasmid genes encoding resistance to cadmium, zinc, and cobalt in Alcaligenes eutrophus CH34.
- ION ANTAGONISMS IN MICROORGANISMS: INTERFERENCE OF NORMAL MAGNESIUM METABOLISM BY NICKEL, COBALT, CADMIUM, ZINC, AND MANGANESE