Winkler H H
J Bacteriol. 1971 May;106(2):362-8. doi: 10.1128/jb.106.2.362-368.1971.
Efflux and the steady state in a group translocation system, the alpha-methylglucoside (alphaMG) transport system, were investigated. The maximum intracellular level of alpha-methylglucoside is a function of a steady state. There is no inhibition of alphaMG influx as the intracellular pool of alphaMG, and alpha-methylglucoside-6-phosphate (alphaMGP) rises. This steady state has three components: alphaMG influx, action of an alphaMGP phosphatase, and alphaMG efflux. The phosphatase is the rate-limiting step (half-time = 5.0 min); thus, the true efflux rate (half-time = 2.0 min) cannot be simply measured from the kinetics of alphaMG loss from the cell. Under our steady-state conditions the percentage of intracellular radioactivity present as alphaMGP was 71%. Under conditions of zero influx, after an efflux of 12 min the percentage present as alphaMGP fell to 55%. However, when fluoride was present during the efflux period, the percentage of the sugar as alphaMGP increased to about 85%. Fluoride greatly inhibits both influx and phosphatase activity (half-time = 50 min). The efflux of alphaMG from the cell is apparently also fluoride-sensitive but to a lesser extent (half-time = 4.1 min). These data are summarized in a model describing the three components of the steady-state and effect of fluoride.
研究了基团转移系统（α-甲基葡萄糖苷（αMG）转运系统）中的外排和稳态。α-甲基葡萄糖苷的最大细胞内水平是稳态的一个函数。随着α-甲基葡萄糖苷和α-甲基葡萄糖苷-6-磷酸（αMGP）的细胞内池增加，αMG内流没有受到抑制。这个稳态有三个组成部分：αMG内流、αMGP磷酸酶的作用和αMG外排。磷酸酶是限速步骤（半衰期 = 5.0分钟）；因此，不能简单地从细胞中αMG损失的动力学来测量真正的外排速率（半衰期 = 2.0分钟）。在我们的稳态条件下，以αMGP形式存在的细胞内放射性百分比为71%。在零内流条件下，外排12分钟后，以αMGP形式存在的百分比降至55%。然而，当在外排期间存在氟化物时，作为αMGP的糖的百分比增加到约85%。氟化物极大地抑制内流和磷酸酶活性（半衰期 = 50分钟）。αMG从细胞中的外排显然也对氟化物敏感，但程度较小（半衰期 = 4.1分钟）。这些数据总结在一个描述稳态的三个组成部分和氟化物作用的模型中。
