蕈状支原体山羊亚种中的活性钾离子转运。净钾离子和单向钾离子移动。

Active K+ transport in Mycoplasma mycoides var. Capri. Net and unidirectional K+ movements.

作者信息

Leblanc G, Le Grimellec C

出版信息

Biochim Biophys Acta. 1979 Jun 13;554(1):156-67. doi: 10.1016/0005-2736(79)90015-4.

Abstract

Analysis of the cation composition of growing Mycoplasma mycoides var. Capri indicates that these organisms have a high intracellular K+ concentration (Ki: 200--300 mM) which greatly exceeds that of the growth medium, and a low Na+ concentration (Na+i: 20 mM). Unlike Na+i,K+i varies with cell aging. The K+ transport properties studied in washed organisms resuspended in buffered saline solution show that cells maintain a steady and large K+ concentration gradient across their membrane at the expense of metabolic energy mainly derived from glycolysis. In starved cells, K+i decreases and is partially compensated by a gain in Na+. This substitution completely reverses when metabolic substrate is added (K+ reaccumulation process). Kinetic analysis of K+ movement in cells with steady K+ level shows that most of K+ influx is mediated by an autologous K+-K+ exchange mechanism. On the other hand, during K+ reaccumulation by K+-depleted cells, a different mechanism (a K+ uptake mechanism) with higher transport capacity and affinity drives the net K+ influx. Both mechanisms are energy-dependent. Ouabain and anoxia have no effect on K+ transport mechanisms; in contrast, both processes are completely blocked by dicyclohexylcarbodiimide, an inhibitor of the Mg2+ -dependent ATPase activity.

摘要

对生长中的丝状支原体山羊亚种的阳离子组成分析表明，这些生物体具有较高的细胞内K⁺浓度（Ki：200 - 300 mM），大大超过生长培养基中的浓度，且Na⁺浓度较低（Na⁺i：20 mM）。与Na⁺i不同，K⁺i随细胞衰老而变化。在缓冲盐溶液中重悬的洗涤过的生物体中研究的K⁺转运特性表明，细胞以主要源自糖酵解的代谢能量为代价，在其膜上维持稳定且较大的K⁺浓度梯度。在饥饿细胞中，K⁺i降低，并部分由Na⁺的增加所补偿。当添加代谢底物时（K⁺再积累过程），这种替代完全逆转。对K⁺水平稳定的细胞中K⁺运动的动力学分析表明，大多数K⁺内流是由自体K⁺ - K⁺交换机制介导的。另一方面，在K⁺耗尽的细胞进行K⁺再积累期间，一种具有更高转运能力和亲和力的不同机制（一种K⁺摄取机制）驱动净K⁺内流。两种机制均依赖能量。哇巴因和缺氧对K⁺转运机制没有影响；相反，这两个过程都被二环己基碳二亚胺完全阻断，二环己基碳二亚胺是一种Mg²⁺依赖性ATP酶活性的抑制剂。