毒素分泌
中文名称
通路描述
毒素是宿主代谢具有最强直接效应的毒力因子。毒素的表达及其分泌机器的结合，会将任何共生菌转化为病原体。在肠杆菌中，毒素和支持基因可以位于染色体基因组或质粒上。在两种情况下，它们也可以作为原病毒的组成部分。这意味着大多数毒素的毒力是可转移的，其分类范围取决于相应移动元件的分类特异性（Sonea, 1987）。
肠杆菌中存在几种类型的毒素。热不稳定肠毒素（LT）属于AB5 类型的毒素，存在于许多肠杆菌以外的病原体中，形成异六聚体蛋白复合物。相比之下，热稳定肠毒素（ST）是小的蛋白质单体。大多数两种毒素类型成员的基因都可以位于移动元件上，并不局限于特定的菌株（Turner et al, 2006; Wang et al, 2019）。LT 通过细菌外膜的导出由 II 型分泌系统（Mudrak & Kuehn, 2010）促进。ST 蛋白由包含 TolC 孔的出液泵复合物导出（Zhu et al, 2018）。
肠致病菌性大肠杆菌对宿主细胞的毒性机制包括 LT 激活腺苷酸环化酶和 ST 激活鸟苷酸环化酶 C，导致离子通道打开，随后引起腹泻（综述 Zhang et al., 2022）。肠外致病菌性大肠杆菌菌株也可能分泌蛋白酶；它们的宿主相互作用在很大程度上是未知的（综述 Tapader et al., 2019）。
肠杆菌中存在几种类型的毒素。热不稳定肠毒素（LT）属于AB5 类型的毒素，存在于许多肠杆菌以外的病原体中，形成异六聚体蛋白复合物。相比之下，热稳定肠毒素（ST）是小的蛋白质单体。大多数两种毒素类型成员的基因都可以位于移动元件上，并不局限于特定的菌株（Turner et al, 2006; Wang et al, 2019）。LT 通过细菌外膜的导出由 II 型分泌系统（Mudrak & Kuehn, 2010）促进。ST 蛋白由包含 TolC 孔的出液泵复合物导出（Zhu et al, 2018）。
肠致病菌性大肠杆菌对宿主细胞的毒性机制包括 LT 激活腺苷酸环化酶和 ST 激活鸟苷酸环化酶 C，导致离子通道打开，随后引起腹泻（综述 Zhang et al., 2022）。肠外致病菌性大肠杆菌菌株也可能分泌蛋白酶；它们的宿主相互作用在很大程度上是未知的（综述 Tapader et al., 2019）。
英文描述
Secretion of toxins Toxins are the virulence factors with the strongest direct effect on host metabolism. Expression of a toxin, together with its secretion machinery, changes any commensal organism into a pathogen. In enterobacteria, toxin and supportive genes can be located on the chromosomal genome or on a plasmid. In both cases they can also be part of a provirus. This means for most toxins that virulence is transferable, and its taxonomic range depends on the taxonomic specificity of the respective mobile element (Sonea, 1987).
Several types of toxins are found in enterobacteria. Heat-labile enterotoxins (LT) belong to the AB5 type of toxins present in many pathogens outside the enterobacteria, forming a heterohexamer protein complex. Heat-stable enterotoxins (ST) in contrast are small protein monomers. Genes of most members of both toxin types can be found on mobile elements, and are not restricted to specific strains (Turner et al, 2006; Wang et al, 2019). Export of LT through the bacterial outer membrane is facilitated by the type II secretion system (Mudrak & Kuehn, 2010). ST proteins get exported by an efflux-pump complex containing the TolC pore (Zhu et al, 2018).
Mechanisms of enteropathogenic E.coli toxicity to the host cell include activation of adenylate cyclase by LT and of guanylate cyclase C by ST, causing the opening of ion channels and subsequent diarrhea (reviewed by Zhang et al., 2022). Extraintestinal pathogenic E.coli strains may also secrete proteases; their host interactions are largely unknown (reviewed in Tapader et al., 2019).
Several types of toxins are found in enterobacteria. Heat-labile enterotoxins (LT) belong to the AB5 type of toxins present in many pathogens outside the enterobacteria, forming a heterohexamer protein complex. Heat-stable enterotoxins (ST) in contrast are small protein monomers. Genes of most members of both toxin types can be found on mobile elements, and are not restricted to specific strains (Turner et al, 2006; Wang et al, 2019). Export of LT through the bacterial outer membrane is facilitated by the type II secretion system (Mudrak & Kuehn, 2010). ST proteins get exported by an efflux-pump complex containing the TolC pore (Zhu et al, 2018).
Mechanisms of enteropathogenic E.coli toxicity to the host cell include activation of adenylate cyclase by LT and of guanylate cyclase C by ST, causing the opening of ion channels and subsequent diarrhea (reviewed by Zhang et al., 2022). Extraintestinal pathogenic E.coli strains may also secrete proteases; their host interactions are largely unknown (reviewed in Tapader et al., 2019).
所含基因
1 个基因