Salmonella type III secretion-associated chaperones confer secretion-pathway specificity
Salmonella type III secretion-associated chaperones confer secretion-pathway specificity
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DOI：
10.1046/j.1365-2958.2003.03840.x
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发表时间：
2004-01-01
影响因子：
3.6
通讯作者：
Galán, JE
中科院分区：
文献类型：
--
作者：
Lee, SH;Galán, JE
III型蛋白质分泌系统（TTSS）与鞭毛输出系统有祖先关系，并且对于许多对人类、动物和植物致病的细菌的毒力是必需的。大多数注定要通过TTSS途径的蛋白质具有至少两个结构域，其特异性地将它们靶向分泌器。其中一个结构域位于氨基末端的第一个类似于20个氨基酸的区域内，第二个结构域位于第一个类似于140个氨基酸的区域内，作为特异性伴侣的结合位点。先前已经提出，这两种分泌信号能够彼此独立地操作以促进分泌到细胞外环境中。我们已经发现，在其分子伴侣结合结构域的情况下，鼠伤寒沙门氏菌TTSS分泌的蛋白SptP和SopE不再通过其同源TTSS分泌，而是通过鞭毛输出途径分泌。这些结果表明，存在一个'祖先'鞭毛分泌信号内TTSS-出口的蛋白质，揭示了在伴侣结合结构域的情况下。此外，我们发现，分泌到培养上清液以及易位到宿主细胞的同源TTSS需要两个，氨基末端和伴侣结合结构域。我们从这些研究中得出结论，TTSS相关分子伴侣的关键功能是赋予其同源分泌蛋白的分泌途径特异性。
Type III protein secretion systems (TTSSs) are ancestrally related to the flagellar export system and are essential for the virulence of many bacteria pathogenic for humans, animals and plants. Most proteins destined to travel the TTSS pathway possess at least two domains that specifically target them to the secretion apparatus. One of the domains is located within the amino terminal first similar to20 amino acids and the second domain, located within the first similar to140 amino acids, serves as a binding site for specific chaperones. It has been previously proposed that these two secretion signals are capable of operating independently of one another to facilitate secretion into the extracellular environment. We have found that in the absence of their chaperone-binding domains, the Salmonella typhimurium TTSS-secreted proteins SptP and SopE are no longer targeted for secretion through their cognate TTSS and, instead, are secreted through the flagellar export pathway. These results indicate the existence of an 'ancestral' flagellar secretion signal within TTSS-exported proteins that is revealed in the absence of the chaperone-binding domain. Furthermore, we found that secretion into culture supernatants as well as translocation into host cells by the cognate TTSS require both, the amino terminal and chaperone-binding domains. We conclude from these studies that a critical function for the TTSS-associated chaperones is to confer secretion-pathway specificity to their cognate secreted proteins.