细菌毒素-抗毒素系统的研究进展

毒素-抗毒素系统(toxin-antitoxin system,TA)由两个共表达的基因组成,其中一个基因编码不稳定的抗毒素蛋白(antitoxin),另一个基因编码稳定的毒素蛋白(toxin).毒素-抗毒素系统最早发现于一些低拷贝的质粒,用来维持低拷贝质粒在菌群中的稳定存在.随后的研究表明,毒素-抗毒素系统广泛存在于细菌,包括一些致病菌的染色体上.在营养缺乏等不良生长条件下,由于基因表达的抑制和蛋白酶的降解作用,不稳定的抗毒素蛋白减少,从而产生游离的毒素蛋白,导致细菌的生长抑制和死亡.毒素-抗毒素系统的生理功能目前还存在争议,有学者认为细茼染色体上的毒素-抗毒素系统可以在不良生长状况下介导细菌的死亡,即细茼程序性细胞死亡(baeterial programmedcell death).但也有证据显示,毒素-抗毒素系统的功能更偏向于应激状态下的生理调节方面,即只起应激状态下的抑菌作用而不是杀菌作用.对细菌生长调控中毒素-抗毒素系统的作用机理进行综述,并探讨毒素-抗毒素系统研究的理论和应用价值.

Progress in The Study of Bacterial Toxin-antitoxin System

The toxin-antitoxin (TA) system consists of a pair of co-expressed genes. The upstream gene encodes an unstable antitoxin protein, and the downstream gene encodes a stable toxin. The toxin-antitoxin system was originally found on the low-copy plasmid to maintenance the plasmid stability. Recently the TA loci have been widely identified on the chromosomes of bacteria, including the some pathogens. The TA systems play an important role in the bacterial growth control or the bacterial programmed cell death under starvation and other stress conditions. The toxin in different TA system has different cellular targets. CcdB toxin in the ccdAB system interacts with the catalytic GyrA subunit of gyrase to inhibit the DNA replication. RelE toxin in the relBE system assists the RNA cleavage at the ribosome A site with a high coden specificity. PemK toxin in the pemIK system and MazF toxin in the mazEF system are identified as endoribonucleases, which cleave the cellular mRNA in a sequence-specific manner to interfere with mRNA function and inhibit the protein synthesis. This review summarizes the mechanism of the toxin in TA system and evaluates the applications of TA system in the future.