The poison–antidote stability system of the broad‐host‐range Thiobacillus ferrooxidans plasmid pTF‐FC2
The poison–antidote stability system of the broad‐host‐range Thiobacillus ferrooxidans plasmid pTF‐FC2
复制标题
广宿主范围氧化亚铁硫杆菌质粒pTF-FC2的毒解毒稳定性系统
作者：
Anthony S. G. Smith;D. Rawlings
在质粒pTF-FC 2中，三个小的开放阅读框（ORF）位于其IncQ-型复制子的repB（引发酶）基因和repA（解旋酶）基因之间。三个ORF中的每一个的破坏，随后进行质粒稳定性和宿主细胞生长的测试表明，ORF编码的毒物解毒剂质粒稳定性系统。这三个基因被命名为pasA、pasB和pasC（质粒成瘾系统），其中PasA是解毒剂，PasB是毒素，PasC是一种蛋白质，似乎可以增强解毒剂中和毒素的能力。pasA基因的破坏导致两种不同的自发缺失，其使稳定性系统失活，但不改变宿主范围或质粒拷贝数。这表明这三个小ORF不参与质粒复制。当置于tac启动子之后时，发现pasB的诱导对宿主细胞具有高度致死性，这表明Pas系统通过杀死无质粒的宿主细胞而不是通过阻滞无质粒的分离体的生长来起作用，如在R1的ParD系统中发生的那样。尽管如此，Pas毒物-解毒剂系统的存在导致pTF-FC 2宿主复制子的相对适度的三倍稳定性和不稳定的异源R1质粒复制子的稳定性的类似增加。Pas系统是一种解毒剂质粒稳定性模块，似乎已整合到pTF-FC 2复制子模块中。
In plasmid pTF‐FC2, three small open reading frames (ORFs) are situated between the repB (primase) gene and the repA (helicase) gene of its IncQ‐type replicon. Disruption of each of the three ORFs followed by tests for plasmid stability and host cell growth indicated that the ORFs encoded a poison–antidote plasmid stability system. The three genes were named pasA, pasB and pasC (plasmid addiction system), in which PasA is the antidote, PasB the toxin and PasC a protein that appears to enhance the ability of the antidote to neutralize the toxin. Disruption of the pasA gene resulted in two different spontaneous deletions, which inactivated the stability system but did not alter the host range or plasmid copy number. This indicated that the three small ORFs were not involved in plasmid replication. When placed behind a tac promoter, induction of pasB was found to be highly lethal to host cells, which suggests that the Pas system acts by killing plasmid‐free host cells rather than by retarding the growth of plasmid‐free segregants, as occurs in the ParD system of R1. In spite of this, the presence of the Pas poison–antidote system resulted in a relatively modest threefold stabilization of the pTF‐FC2 host replicon and a similar increase in the stabilization of an unstable heterologous R1 plasmid replicon. The Pas system is a poison–antidote plasmid stability module, which appears to have become integrated within the pTF‐FC2 replicon module.
影响因子：
5.6
作者：
ROBERTS, RC;STROM, AR;HELINSKI, DR
通讯作者：
HELINSKI, DR