乳酸链球菌对铊离子的主动转运

Active transport of thallous ions by Streptococcus lactis.

作者信息

Kashket E R

出版信息

J Biol Chem. 1979 Sep 10;254(17):8129-31.

Abstract

Tl+ ions have been shown to mimic or compete with K+ in a number of membrane systems. We confirmed that in starved, valinomycin-treated cells of Streptococcus lactis 7962, Tl+ ions distributed themselves across the bacterial membrane in response to the potassium diffusion potential. In glucose-energized cells, however, Tl+ was taken up by a system specifically stimulated by sodium salts. The intracellular levels of Tl+ exceeded those attained by [3H]triphenylmethylphosphonium ion, a lipophilic cation which accumulates in response to the membrane potential. The uptake of Tl+ by (Na+ and glucose)-stimulated cells was strongly inhibited by potassium salts. These experiments suggest that metabolic energy is coupled to Tl+ transport by means of a high energy phosphate compound and that Tl+ ions are actively transported by a membrane carrier whose normal substrate is K+. The uptake of Tl+ is not a valid method for determining the streptococcal membrane potential.

摘要

在许多膜系统中，铊离子（Tl⁺）已被证明可模拟或与钾离子（K⁺）竞争。我们证实，在饥饿的、经缬氨霉素处理的乳酸链球菌7962细胞中，Tl⁺离子会根据钾离子扩散电位分布于细菌膜上。然而，在葡萄糖供能的细胞中，Tl⁺会被一种由钠盐特异性刺激的系统摄取。Tl⁺的细胞内水平超过了[³H]三苯甲基鏻离子所达到的水平，[³H]三苯甲基鏻离子是一种亲脂性阳离子，会根据膜电位进行积累。钾盐强烈抑制（钠离子和葡萄糖）刺激的细胞对Tl⁺的摄取。这些实验表明，代谢能量通过一种高能磷酸化合物与Tl⁺转运相偶联，并且Tl⁺离子由一种正常底物为K⁺的膜载体进行主动转运。摄取Tl⁺并非测定链球菌膜电位的有效方法。