FEBS Letters | |
A novel antiporter activity catalyzing sodium and potassium transport from right‐side‐out vesicles of E. coli | |
Verkhovskaya, Marina L.1  Verkhovsky, Michael I.1  Wikström, Mårten1  | |
[1] Helsinki Bioenergetics Group, Institute of Biomedical Sciences, Department of Medical Chemistry, P. O. Box 8, 00014 University of Helsinki, Helsinki, Finland | |
关键词: Na+ transport; K+ transport; E. coli; MOPS; 4-morpholinepropanesulfonic acid; MES; 2-[N-morpholino]ethanesulfonic acid; tricine; N-tris[hydroxymethyl]methylglycine; ΔΨ transmembrane difference in electric potential; ΔpH; transmembrane chemical gradient of H+; ΔpNa; transmembrane chemical gradient of Na+; TPP+; tetraphenylphosphonium cation; | |
DOI : 10.1016/0014-5793(95)00281-D | |
学科分类:生物化学/生物物理 | |
来源: John Wiley & Sons Ltd. | |
【 摘 要 】
Downhill sodium efflux from right-side-out E. coli membrane vesicles was found to be stimulated by negative electric potential, as has been reported earlier [Bassilana et al., Biochemistry 23 (1984) 1015–1022], and in agreement with the concept of electrogenic Na+/nH+ antiporters with n < 1. However, sodium efflux was much more accelerated by positive electric potential, indicating the operation of another sodium transport system. ΔpH (alkaline inside), created by a pH shift from 8.5 to 6.8 in the medium was found to drive sodium efflux against its concentration gradient, but only when the vesicles had been loaded with both Na+ and K+. Efflux of K+ against the concentration gradient was also observed under these conditions. When the vesicles were loaded separately with sodium tricine or potassium tricine, no K+ efflux and insignificant Na+ efflux were observed. We propose that there are at least two different mechanisms responsible for Na+ efflux in E. coli vesicles. One is the Na+/nH+ antiporter previously described, and the other is a novel Na+,K+/mH+ antiporter.
【 授权许可】
Unknown
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