细菌钠离子输出系统的类型及其可能机制

Sodium ion transportation system and its possible mechanisms in Bacteria

摘要:

在高盐条件下,绝大多数微生物通过拒盐策略适应其生存环境,其中,钠离子输出系统在维持细胞正常的盐浓度和pH稳态等生命活动过程中扮演十分重要的角色。细菌的钠离子输出系统包括初级钠泵和次级钠泵两种类型,前者所介导的钠离子输出与呼吸相偶联,后者又分为单亚基和多亚基两种类型。到目前为止,有关初级钠泵和次级钠泵转运钠离子的分子机制还停留在推测阶段。对细菌Na+输出系统的类型和Na+外排的可能机制进行综述,并对有待深入研究的问题进行探讨。

Abstract:

Sodium ion with high concentration is toxic to living cells, and microorganisms adapt to the environment containing high concentration of salt by the strategies of salt-in-cytoplasm and compatible solutes. The Na＋ extrusion system plays important roles in maintaining cytoplasmic Na^＋ homeostasis and pH level in microbial cells. Two possible mechanisms of Na⁺ circulation across the cytoplasmic membrane have been proposed, namely primary Na⁺ pump and secondary Na⁺/H⁺ antiporter. Primary sodium pumps coupled the extrusion of Na^＋ to respiration, and the activity of which was insensitive to uncoupler CCCP (carbonyl-cyanide m-chlorophenylhydrazone). There were two types of secondary Na⁺/H⁺ antiporters-encoding genes designated single gene and multiple subunits, respectively. The types of transportation systems for Na^＋, possible mechanisms of Na^＋ extrusion, and projects for further study in bacteria are reviewed.