Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
J Biol Chem. 2010 Apr 30;285(18):13357-63. doi: 10.1074/jbc.M109.094045. Epub 2010 Mar 8.
Salmonella enterica serovar Typhimurium invade non-phagocytic cells by injecting bacterial effector proteins to exploit the host actin cytoskeleton network. SipC is such a Salmonella effector known to nucleate actin, bundle F-actin, and translocate type III effectors. The molecular mechanism of how SipC bundles F-actin and SipC domains responsible for these activities are not well characterized. We successfully separated these activities through a series of genetic deletion/insertions in SipC. We found that the C terminus (amino acids 200-409) of SipC bundled actin filaments using in vitro biochemical assays. We further demonstrated that amino acid residues 221-260 and 381-409 of full-length SipC were indispensable for its actin binding and bundling activities. Furthermore, Salmonella mutant strains lacking the actin bundling activity were less invasive into HeLa cells. These studies indicate that the C terminus of SipC bundles F-actin to promote Salmonella invasion.
肠炎沙门氏菌血清型 Typhimurium 通过注射细菌效应蛋白来利用宿主肌动蛋白细胞骨架网络入侵非吞噬细胞。SipC 是一种已知的沙门氏菌效应蛋白，能够引发肌动蛋白聚合、束状 F-肌动蛋白和转位 III 型效应蛋白。SipC 束状 F-肌动蛋白的分子机制以及负责这些活性的 SipC 结构域尚未得到很好的描述。我们通过在 SipC 中进行一系列基因缺失/插入成功分离了这些活性。我们发现 SipC 的 C 端（氨基酸 200-409）在体外生化测定中束状肌动蛋白丝。我们进一步证明全长 SipC 的氨基酸残基 221-260 和 381-409 对于其肌动蛋白结合和束状活性是必不可少的。此外，缺乏肌动蛋白束状活性的沙门氏菌突变株对 HeLa 细胞的侵袭性降低。这些研究表明 SipC 的 C 端束状 F-肌动蛋白以促进沙门氏菌的侵袭。
