质子偶联转运系统的定量分析。大肠杆菌中的β-半乳糖苷外排
Quantitative analysis of proton-linked transport system. beta-Galactoside exit in Escherichia coli.
作者信息
Booth I R, Hamilton W A
出版信息
Biochem J. 1980 May 15;188(2):467-73. doi: 10.1042/bj1880467.
The exit of lactose and thiomethyl-beta-D-galactoside from Escherichia coli ML308-225 has been studied to determine the role of carrier-dependent (zero-trans efflux) and carrier-independent (leak) processes. On the basis of its sensitivity to p-chloromercuribenzene sulphonate the exit of lactose was found to be almost wholly mediated by the carrier. Consistent with this conclusion was the finding that the rate of exit of this sugar was dependent on the external pH, being considerably slower at acid pH. On the other hand exit of thiomethyl-beta-D-galactoside was found to be composed of both carrier-dependent and carrier-independent processes. Both processes exhibited first-order kinetics with the rate constants for zero-trans efflux and leak being 0.137 min-1 and 0.079 min-1, respectively. The relevance of these findings for out earlier proposal for the methods of attenuation of solute accumulation is discussed [Booth, Mitchell & Hamilton (1979) Biochem. J. 182, 687--696].
对乳糖和硫代甲基-β-D-半乳糖苷从大肠杆菌ML308 - 225中的排出进行了研究，以确定载体依赖性（零转运流出）和载体非依赖性（渗漏）过程的作用。基于其对对氯汞苯磺酸盐的敏感性，发现乳糖的排出几乎完全由载体介导。与此结论一致的是，发现这种糖的排出速率取决于外部pH值，在酸性pH值下排出速度明显较慢。另一方面，发现硫代甲基-β-D-半乳糖苷的排出由载体依赖性和载体非依赖性过程组成。这两个过程均表现出一级动力学，零转运流出和渗漏的速率常数分别为0.137 min⁻¹和0.079 min⁻¹。讨论了这些发现与我们早期提出的溶质积累衰减方法的相关性[Booth，Mitchell和Hamilton（1979年）《生物化学杂志》182，687 - 696]。
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