期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：8
页码：3167-3170
DOI：10.1073/pnas.74.8.3167
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Membrane vesicles prepared from Escherichia coli B/r grown on glutamate as a sole source of carbon and energy require sodium for glutamate accumulation when energized by D-lactate oxidation. Glutamate uptake can also be driven by a prearranged sodium gradient (out to in) in the absence of an energy source or a protonmotive force. Sodium ions are exchanged rapidly in respiring vesicles and the sodium gradient may be large enough under certain conditions to drive glutamate uptake after the protonmotive force is abolished with m-chlorocarbonylcyanide phenylhydrazone. Glutamate uptake due to a prearranged sodium gradient or lactate oxidation is inhibited by monensin but not by nigericin. Transport does not occur in response to valinomycin-induced membrane potential. We interpret these results to indicate that glutamate transport is obligately coupled to sodium transport and can only occur when there is a net flux of sodium ions. This flux is driven by a chemical gradient of sodium that is created by the protonmotive force generated by respiration.
