The respiration‐driven active sodium transport system in E. coli does not function with lithium

Publisher Website
Google Scholar
Abstract
Comparison of respiration‐driven active transport of alkali cations from E. coli cells loaded with Na+ or Li+ showed that Li+ could not be expelled from the cells like Na+. K+ accumulation, which was fast in Na+‐loaded cells, was strongly inhibited in Li+‐loaded cells, despite high membrane potential and respiratory rate. When Li+‐loaded cells were placed into medium containing Na+ instead of Li+, Li+/Na+ exchange took place initially, while K+ accumulation was delayed. Only after almost all inside Li+ was replaced by Na+ did active Na+ and K+ transport commence. These data confirm that it is a distinct active sodium transport system (AST) with Na+,K+/H+ antiporter activity, and not the Na+/H+ antiporters, that is responsible for active Na+ transport in E. coli [Verkhovskaya, M.L., Verkhovsky, M.I. and Wikström, M. (1996) Biochim. Biophys. Acta 1273, 207–216]. In contrast to the Na+/H+ antiporters, the AST system is inhibited by Li+.