Holin-Dependent Secretion of the Large Clostridial Toxin TpeL by Clostridium perfringens.
Holin-Dependent Secretion of the Large Clostridial Toxin TpeL by Clostridium perfringens.
复制标题
产气荚膜梭菌对大梭菌毒素 TpeL 的穴蛋白依赖性分泌。
DOI：
10.1128/jb.00580-20
复制
发表时间：
2021
影响因子：
3.2
通讯作者：
Melville,StephenB
中科院分区：
文献类型：
--
作者：
Saadat,Angela;Melville,StephenB
大梭菌毒素（LCT）是在几个物种中发现的分泌型毒力因子，包括艰难梭菌、产气荚膜梭菌、索氏类梭菌和诺氏梭菌。LCT是缺乏分泌信号序列的大型毒素，其他人的研究表明，C.艰难梭菌TcdA和TcdB的分泌需要holin样蛋白TcdE。TcdE基因定位于C.艰难梭菌和holin编码基因也存在于来自Sordellii和C.产气荚膜杆菌然而，与C.产气荚膜杆菌LCT TpeL与TcdE没有同源性并且具有不同的膜拓扑结构。此外，TpeE具有与TatA蛋白相同的膜拓扑结构，TatA蛋白是双精氨酸易位（达特）分泌系统的核心。为了确定TpeE是否是分泌TpeL所必需的和足够的，从C型C菌株的基因。产气荚膜梭菌在A型菌株中表达。使用蛋白质印迹法测量产气荚膜杆菌、HN 13和分泌。我们发现TpeL分泌需要TpeE，并且分泌不是由于细胞裂解。缺乏两亲性螺旋和带电C-末端结构域的TpeE的突变形式不能分泌TpeL，并且删除TpeL中保守的LCT结构域的突变表明只能分泌全长蛋白。总之，我们已经确定了一个新的家族的holin样蛋白，可以发挥作用，在某些情况下，作为一个系统的蛋白分泌的蛋白质，需要折叠在cytoplasm.IMPORTANCELittle的机制，LCT的分泌。由于LCT是梭菌病原体的主要毒力因子，我们想确定LCT在梭菌中的作用机制。产气荚膜杆菌TpeL由与先前描述的分泌相关孔蛋白缺乏同源性的蛋白质（TpeE）分泌。我们发现，TpeE是一个广泛分布的一类holin蛋白的成员，和TpeE是必要的分泌TpeL。TpeE在膜拓扑结构上与TatA蛋白具有高度相似性，TatA蛋白形成孔，达特分泌底物通过该孔穿过细胞质膜。因此，TpeE-TpeL分泌系统可能是一个模型，不仅可以理解holin依赖性分泌，但也如何TatA蛋白在分泌过程中的功能。
Large clostridial toxins (LCTs) are secreted virulence factors found in several species, including Clostridioides difficile, Clostridium perfringens, Paeniclostridium sordellii, and Clostridium novyi. LCTs are large toxins that lack a secretion signal sequence, and studies by others have shown that the LCTs of C. difficile, TcdA and TcdB, require a holin-like protein, TcdE, for secretion. The TcdE gene is located on the pathogenicity locus (PaLoc) of C. difficile, and holin-encoding genes are also present in the LCT-encoded PaLocs from P. sordellii and C. perfringens. However, the holin (TpeE) associated with the C. perfringens LCT TpeL has no homology and a different membrane topology than TcdE. In addition, TpeE has a membrane topology identical to that of the TatA protein, which is the core of the twin-arginine translocation (Tat) secretion system. To determine if TpeE was necessary and sufficient to secrete TpeL, the genes from a type C strain of C. perfringens were expressed in a type A strain of C. perfringens, HN13, and secretion was measured using Western blot methods. We found that TpeE was required for TpeL secretion and that secretion was not due to cell lysis. Mutant forms of TpeE lacking an amphipathic helix and a charged C-terminal domain failed to secrete TpeL, and mutations that deleted conserved LCT domains in TpeL indicated that only the full-length protein could be secreted. In summary, we have identified a novel family of holin-like proteins that can function, in some cases, as a system of protein secretion for proteins that need to fold in the cytoplasm.IMPORTANCELittle is known about the mechanism by which LCTs are secreted. Since LCTs are major virulence factors in clostridial pathogens, we wanted to define the mechanism by which an LCT in C. perfringens, TpeL, is secreted by a protein (TpeE) lacking homology to previously described secretion-associated holins. We discovered that TpeE is a member of a widely dispersed class of holin proteins, and TpeE is necessary for the secretion of TpeL. TpeE bears a high degree of similarity in membrane topology to TatA proteins, which form the pore through which Tat secretion substrates pass through the cytoplasmic membrane. Thus, the TpeE-TpeL secretion system may be a model for understanding not only holin-dependent secretion but also how TatA proteins function in the secretion process.