Florek Patrik, Muchová Katarína, Pavelcíková Pamela, Barák Imrich
FEMS Microbiol Lett. 2008 Jan;278(2):177-84. doi: 10.1111/j.1574-6968.2007.00984.x.
SpoIISA and SpoIISB proteins from Bacillus subtilis belong to a recently described bacterial programmed-cell death system. The current work demonstrates that the toxin-antitoxin module is also functional in Escherichia coli cells, where the expression of SpoIISA toxin leads to transient growth arrest coupled with cell lysis, and SpoIISA-induced death can be prevented by coexpression of its cognate antitoxin, SpoIISB. Escherichia coli cells appear to be able to escape the SpoIISA killing by activation of a specific, as yet unidentified protease that cleaves out the cytosolic part of the protein. Analysis of the toxic effects of the transmembrane and cytosolic portions of SpoIISA showed that neither of them separately can function as a toxin; therefore, both parts of the protein have to act in concert to exert the killing. This work also identifies genes encoding putative homologues of SpoIISA and SpoIISB proteins on chromosomes of other Bacilli species. The SpoIISA-like proteins from Bacillus anthracis and Bacillus cereus were shown to manifest the same effect on the viability of E. coli as their homologue from B. subtilis. Moreover, expression of the proposed spoIISB-like gene rescues E. coli cells from death induced by the SpoIISA homologue.
来自枯草芽孢杆菌的SpoIISA和SpoIISB蛋白属于最近描述的一种细菌程序性细胞死亡系统。目前的研究表明，这种毒素-抗毒素模块在大肠杆菌细胞中也具有功能，在该细胞中，SpoIISA毒素的表达会导致短暂的生长停滞并伴有细胞裂解，而SpoIISA诱导的死亡可以通过共表达其同源抗毒素SpoIISB来预防。大肠杆菌细胞似乎能够通过激活一种特定的、尚未鉴定的蛋白酶来逃避SpoIISA的杀伤，该蛋白酶可切割掉该蛋白的胞质部分。对SpoIISA跨膜和胞质部分的毒性作用分析表明，它们单独都不能作为毒素发挥作用；因此，该蛋白的两个部分必须协同作用才能发挥杀伤作用。这项研究还在其他芽孢杆菌属物种的染色体上鉴定出了编码SpoIISA和SpoIISB蛋白假定同源物的基因。炭疽芽孢杆菌和蜡样芽孢杆菌的SpoIISA样蛋白对大肠杆菌活力的影响与其枯草芽孢杆菌同源物相同。此外，所提出的spoIISB样基因的表达可使大肠杆菌细胞免于SpoIISA同源物诱导的死亡。
