Dental Research Institute, Faculty of Dentistry, University of Toronto, 124 Edward Street, Toronto, ON M5G 1G6, Canada.
Can J Microbiol. 2012 May;58(5):553-62. doi: 10.1139/w2012-025. Epub 2012 Apr 16.
Most prokaryotic chromosomes contain a number of toxin-antitoxin (TA) modules consisting of a pair of genes that encode 2 components, a stable toxin and its cognate labile antitoxin. TA systems are also known as addiction modules, since the cells become "addicted" to the short-lived antitoxin product (the unstable antitoxin is degraded faster than the more stable toxin) because its de novo synthesis is essential for their survival. While toxins are always proteins, antitoxins are either RNAs (type I, type III) or proteins (type II). Type II TA systems are widely distributed throughout the chromosomes of almost all free-living bacteria and archaea. The vast majority of type II toxins are mRNA-specific endonucleases arresting cell growth through the mechanism of RNA cleavage, thus preventing the translation process. The physiological role of chromosomal type II TA systems still remains the subject of debate. This review describes the currently known type II toxins and their characteristics. The different hypotheses that have been proposed to explain their role in bacterial physiology are also discussed.
大多数原核生物染色体包含多个毒素-抗毒素（TA）模块，这些模块由一对基因组成，编码两种成分，一种稳定的毒素及其同源不稳定的抗毒素。TA 系统也被称为成瘾模块，因为细胞会“依赖”短暂存在的抗毒素产物（不稳定的抗毒素比更稳定的毒素降解得更快），因为它的从头合成对于它们的生存是必不可少的。虽然毒素通常是蛋白质，但抗毒素可以是 RNA（I 型、III 型）或蛋白质（II 型）。II 型 TA 系统广泛分布于几乎所有自由生活的细菌和古菌的染色体中。绝大多数 II 型毒素是特定于 mRNA 的核酸内切酶，通过 RNA 切割的机制阻止细胞生长，从而阻止翻译过程。染色体 II 型 TA 系统的生理作用仍然是一个有争议的问题。这篇综述描述了目前已知的 II 型毒素及其特性。还讨论了为解释它们在细菌生理学中的作用而提出的不同假设。
