Miyamoto H, Ikehara T, Yamaguchi H, Hosokawa K, Yonezu T, Masuya T
J Membr Biol. 1986;92(2):135-50. doi: 10.1007/BF01870703.
Ouabain-insensitive, furosemide-sensitive Rb+ influx (JRb) into HeLa cells was examined as functions of the extracellular Rb+, Na+ and Cl- concentrations. Rate equations and kinetic parameters, including the apparent maximum JRb, the apparent values of Km for the three ions and the apparent Ki for K+, were derived. Results suggested that one unit molecule of this transport system has one Na+, one K+ and two Cl- sites with different affinities, one of the Cl- sites related with binding of Na+, and the other with binding of K+(Rb+). A 1:1 stoichiometry was demonstrated between ouabain-insensitive, furosemide-sensitive influxes of 22Na+ and Rb+, and a 1:2 stoichiometry between those of Rb+ and 36Cl-. The influx of either one of these ions was inhibited in the absence of any one of the other two ions. Monovalent anions such as nitrate, acetate, thiocyanate and lactate as substitutes for Cl- inhibited ouabain-insensitive Rb+ influx, whereas sulfamate and probably also gluconate did not inhibit JRb. From the present results, a general model and a specialized cotransport model were proposed: In HeLa cells, one Na+ and one Cl- bind concurrently to their sites and then one K+(Rb+) and another Cl- bind concurrently. After completion of ion bindings Na+, K+(Rb+) and Cl- in a ratio of 1:1:2 show synchronous transmembrane movements.
研究了哇巴因不敏感、呋塞米敏感的铷离子（Rb⁺）流入HeLa细胞的情况，将其作为细胞外Rb⁺、Na⁺和Cl⁻浓度的函数。推导了速率方程和动力学参数，包括表观最大Rb⁺流入量、三种离子的表观Km值以及K⁺的表观Ki值。结果表明，该转运系统的一个单位分子具有一个Na⁺、一个K⁺和两个亲和力不同的Cl⁻位点，其中一个Cl⁻位点与Na⁺的结合有关，另一个与K⁺（Rb⁺）的结合有关。在哇巴因不敏感、呋塞米敏感的22Na⁺和Rb⁺流入之间显示出1:1的化学计量比，在Rb⁺和36Cl⁻的流入之间显示出1:2的化学计量比。在缺少其他两种离子中的任何一种时，这些离子中任何一种的流入都会受到抑制。单价阴离子如硝酸盐、乙酸盐、硫氰酸盐和乳酸盐作为Cl⁻的替代物会抑制哇巴因不敏感的Rb⁺流入，而氨基磺酸盐以及可能还有葡萄糖酸盐不会抑制Rb⁺流入。根据目前的结果，提出了一个通用模型和一个专门的协同转运模型：在HeLa细胞中，一个Na⁺和一个Cl⁻同时与其位点结合，然后一个K⁺（Rb⁺）和另一个Cl⁻同时结合。离子结合完成后，Na⁺、K⁺（Rb⁺）和Cl⁻以1:1:2的比例进行同步跨膜移动。
