ENTERIC BACTERIA AND OSMOTIC-STRESS - INTRACELLULAR POTASSIUM GLUTAMATE AS A SECONDARY SIGNAL OF OSMOTIC-STRESS
ENTERIC BACTERIA AND OSMOTIC-STRESS - INTRACELLULAR POTASSIUM GLUTAMATE AS A SECONDARY SIGNAL OF OSMOTIC-STRESS
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DOI：
10.1111/j.1574-6968.1990.tb04097.x
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发表时间：
1990-06-01
影响因子：
2.1
通讯作者：
HIGGINS, CF
中科院分区：
文献类型：
--
作者：
BOOTH, IR;HIGGINS, CF
肠道细菌已经进化出一系列令人印象深刻的机制，使细胞能够在截然不同的外部渗透压力下生长。它们有两个相互关联的功能：第一，它们允许细胞保持相对恒定的膨压，这是细胞生长所必需的；第二，它们允许细胞质组成的变化，从而使恢复膨压所需的细胞内渗透压的积累不会损害酶的功能。膨压调节的首要事件是钾及其反离子谷氨酸的受控积累。在高渗透压下，细胞质中谷氨酸钾的水平会损害酶的功能。因此，快速生长依赖于次生反应，主要是相容溶质、甜菜碱(N-三甲基甘氨酸)、脯氨酸和海藻糖的积累。这些溶质的积累是通过运输系统和酶的受控活性来实现的，以响应外部渗透压力的变化。有人提出，在膨压调节过程中谷氨酸钾的积累可以作为激活这些系统的信号[1，2]。这篇简短的综述将考察控制细胞质渗透压平衡的证据是通过感测细胞内钾(和谷氨酸)浓度来实现的。
Enteric bacteria have evolved an impressive array of mechanisms that allow the cell to grow at widely different external osmotic pressures. These serve two linked functions; firstly, they allow the cell to maintain in relatively constant turgor pressure which is essential for cell growth; and secondly they permit changes in cytoplasmic composition such that the accumulation of intracellular osmolytes required to restore turgor pressure does not impair enzyme function. The primary event in turgor regulation is the controlled accumulation of potassium and its counterion glutamate. At high external osmolarities the cytoplasmic levels of potassium glutamate can impair enzyme function. Rapid growth is therefore dependent upon secondary responses, principally the accumulation of compatible solutes, betaine (N-trimethylglycine), proline and trehalose. The accumulation of these solutes is achieved by the controlled activity of transport systems and enzymes in response to changes in external osmotic pressure. It has been proposed that the accumulation of potassium glutamate during turgor regulation acts as a signal for the activation of these systems [1,2]. This brief review will examine the evidence that control over the balance of cytoplasmic osmolytes is achieved by sensing of the intracellular potassium (and glutamate) concentration.