MacDonald R E, Lanyi J K, Greene R V
Proc Natl Acad Sci U S A. 1977 Aug;74(8):3167-70. doi: 10.1073/pnas.74.8.3167.
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.
由在以谷氨酸作为唯一碳源和能源的条件下生长的大肠杆菌B/r制备的膜囊泡，在由D-乳酸氧化供能时，积累谷氨酸需要钠离子。在没有能源或质子动力的情况下，预先建立的钠离子梯度（外向内）也能驱动谷氨酸的摄取。钠离子在进行呼吸作用的囊泡中快速交换，在某些条件下，当用间氯羰基亚胺基苯腙消除质子动力后，钠离子梯度可能大到足以驱动谷氨酸的摄取。由预先建立的钠离子梯度或乳酸氧化引起的谷氨酸摄取被莫能菌素抑制，但不被尼日利亚菌素抑制。缬氨霉素诱导的膜电位不会引发转运。我们对这些结果的解释是，谷氨酸转运必然与钠离子转运偶联，并且只有当存在钠离子净通量时才会发生。这种通量由呼吸作用产生的质子动力所形成的钠离子化学梯度驱动。
