Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America.
PLoS One. 2013;8(3):e60499. doi: 10.1371/journal.pone.0060499. Epub 2013 Mar 27.
The delivery of effector proteins by Salmonella across the host cell membrane requires a subset of effectors secreted by the type III secretion system (TTSS) known as translocators. SipC and SipB are translocator proteins that are inserted into host membranes and presumably form a channel that translocates type III effectors into the host cell. The molecular events of how these translocators insert into the host cell membrane remain unknown. We have previously shown that the SipC C-terminal amino acid region (321-409) is required for the translocation of effectors into host cells. In this study, we demonstrate that the ability to form SipC-SipB complex is essential for their insertion into the host membrane. The SipB-interacting domain of SipC is near its C-terminal amino acid region (340-409). In the absence of SipB, SipC was not detected in the membrane fraction. Furthermore, SipC mutants that no longer interact with SipB are defective in inserting into the host cell membrane. We propose a mechanism whereby SipC binds SipB through its C-terminal region to facilitate membrane-insertion and subsequent translocon formation in the host cell membrane.
沙门氏菌通过宿主细胞膜输送效应蛋白需要一组由 III 型分泌系统 (TTSS) 分泌的称为转运蛋白的效应子。SipC 和 SipB 是插入宿主膜的转运蛋白，推测它们形成一个通道将 III 型效应子转运到宿主细胞中。这些转运蛋白如何插入宿主细胞膜的分子事件仍然未知。我们之前已经表明，SipC C 末端氨基酸区域（321-409）是效应子进入宿主细胞转运所必需的。在这项研究中，我们证明了形成 SipC-SipB 复合物的能力对于它们插入宿主膜是必不可少的。SipC 的 SipB 相互作用结构域位于其 C 末端氨基酸区域附近（340-409）。在没有 SipB 的情况下，SipC 未在膜部分中检测到。此外，不再与 SipB 相互作用的 SipC 突变体在插入宿主细胞膜中存在缺陷。我们提出了一种机制，即 SipC 通过其 C 末端区域与 SipB 结合，以促进膜插入和随后在宿主细胞膜中形成转位器。
