Toxin-Antitoxin Systems on the Large Defense Plasmid pSYSA of Synechocystis sp PCC 6803
Toxin-Antitoxin Systems on the Large Defense Plasmid pSYSA of Synechocystis sp PCC 6803
复制标题
DOI：
10.1074/jbc.m112.434100
复制
发表时间：
2013-03-08
影响因子：
4.8
通讯作者：
Hess, Wolfgang R.
中科院分区：
文献类型：
--
作者：
Kopfmann, Stefan;Hess, Wolfgang R.
细菌毒素-抗毒素（TA）系统是由质粒和染色体基因座编码的遗传元件，通过分离后的杀伤机制介导质粒和基因组岛的维持。TA系统在所有原核生物中存在的数量惊人的高，但蓝藻TA系统已经只有非常差的实验特征。蓝细菌是唯一进行产氧光合作用的原核生物。因此，蓝藻具有高度的生态重要性，被认为是生产生物燃料的前景。在这里，我们提出的sll 7003/ssl 7004 TA系统编码的质粒pSYSA的模式蓝藻集胞藻属PCC 6803涉及Mg 2+依赖的RNA内切酶活性靶向单链RNA区域的分子表征，并证明了四个以上的TA系统编码的100，749 bp的质粒的功能。此外，一个额外的I型，一个额外的II型，和三个独立的TA系统组件上预测的pSYSA，所有这些都出现活跃的判断其表达。通过窝藏至少七个同时活跃的TA系统，pSYSA似乎是迄今为止在这方面研究的所有质粒中最强烈选择的质粒。这些结果指出了pSYSA的高度生物相关性，其编码能力为75%，致力于三种不同的成簇规则间隔短回文重复序列（CRISPR）系统介导抗病毒防御。
Bacterial toxin-antitoxin (TA) systems are genetic elements, which are encoded by plasmid as well as chromosomal loci and mediate plasmid and genomic island maintenance through post-segregational killing mechanisms. TA systems exist in surprisingly high numbers in all prokaryotes, but cyanobacterial TA systems have been only very poorly experimentally characterized so far. Cyanobacteria are the only prokaryotes that perform oxygenic photosynthesis. As such, cyanobacteria are of high ecological importance and are considered promising for the production of biofuels. Here, we present the molecular characterization of the sll7003/ssl7004 TA system encoded on plasmid pSYSA of the model cyanobacterium Synechocystis sp. PCC 6803 as involving a Mg2+-dependent RNA endonuclease activity targeting single-stranded RNA regions and demonstrate the functionality of four more TA systems encoded on this 100,749-bp plasmid. Furthermore, one additional type I, one additional type II, and three freestanding TA system components are predicted on pSYSA, all of which appear active judged by their expression. By harboring at least seven simultaneously active TA systems, pSYSA appears as the plasmid most strongly selected for among all plasmids studied in this respect thus far. These results point to a high biological relevance of pSYSA, whose coding capacity is 75% devoted to three distinct clustered regularly interspaced short palindromic repeats (CRISPR) systems mediating antiviral defense.