细菌钠离子输出系统的类型及其可能机制

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。

Sodium ion transportation system and its possible mechanisms in Bacteria

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.