A novel antiporter activity catalyzing sodium and potassium transport from right‐side‐out vesicles of E. coli

FEBS Letters

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