Evidence for multiple K+ export systems in Escherichia coli.
AUTOR(ES)
Bakker, E P
RESUMO
The role of the K+ transport systems encoded by the kefB (formerly trkB) and kefC (formerly trkC) genes of Escherichia coli in K+ efflux has been investigated. The rate of efflux produced by N-ethylmaleimide (NEM), increased turgor pressure, alkalinization of the cytoplasm, or 2,4-dinitrophenol in a mutant with null mutations in both kef genes was compared with the rate of efflux in a wild-type strain for kef. The results show that these two genes encode the major paths for NEM-stimulated efflux. However, neither efflux system appears to be a significant path of K+ efflux produced by high turgor pressure, by alkalinization of the cytoplasm, or by addition of high concentrations of 2,4-dinitrophenol. Therefore, this species must have at least one other system, besides those encoded by kefB and kefC, capable of mediating a high rate of K+ efflux. The high, spontaneous rate of K+ efflux characteristic of the kefC121 mutation increases further when the strain is treated with NEM. Therefore, the mutational defect that leads to spontaneous efflux in this strain does not abolish the site(s) responsible for the action of NEM.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=212460Documentos Relacionados
- Multiple Paths for Nonphysiological Transport of K+ in Escherichia coli
- Evidence for specificity at an early step in protein export in Escherichia coli.
- Valinomycin-induced cation transport in vesicles does not reflect the activity of K+ transport systems in Escherichia coli.
- Evidence for a coupling of synthesis and export of an outer membrane protein in Escherichia coli.
- Evidence for clonal population structure in Escherichia coli.