The tripartite type III secreton of Shigella flexneri inserts IpaB and IpaC into host membranes.
The tripartite type III secreton of Shigella flexneri inserts IpaB and IpaC into host membranes.
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DOI：
10.1083/jcb.147.3.683
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发表时间：
1999-11-01
期刊：
影响因子：
--
通讯作者：
Sansonetti P
中科院分区：
文献类型：
--
作者：
Blocker A;Gounon P;Larquet E;Niebuhr K;Cabiaux V;Parsot C;Sansonetti P
细菌III型分泌系统用于将蛋白质转运到真核细胞中，需要分泌子和转运蛋白以使蛋白质通过细菌和宿主膜。我们利用福氏志贺菌的接触溶血活性来研究其假定的转运蛋白。溶血是由红细胞（RBC）膜内形成的25 μ m孔引起的。志贺氏菌在激活其III型分泌系统后分泌的五种蛋白中，只有疏水性IpaB和IpaC与溶血后分离的RBC膜紧密相关。ipa蛋白分泌和溶血反应是动力学耦合过程。然而，在不存在离心的情况下，RBC附近的Ipa蛋白分泌不足以引起溶血。除菌作用使细菌与红细胞膜之间的距离降低到临界阈值以上。电子显微镜分析表明，在任何宿主接触之前，分泌子在37 ° C下组成型组装。它们由三部分组成：（a）外部针，（B）颈域，和（c）大的近端球。分泌物形态没有改变后，激活分泌。在突变体的一些基因编码的分泌机制的细胞器是不存在的，而ipaB和ipaC突变体显示正常的分泌。
Bacterial type III secretion systems serve to translocate proteins into eukaryotic cells, requiring a secreton and a translocator for proteins to pass the bacterial and host membranes. We used the contact hemolytic activity of Shigella flexneri to investigate its putative translocator. Hemolysis was caused by formation of a 25-Å pore within the red blood cell (RBC) membrane. Of the five proteins secreted by Shigella upon activation of its type III secretion system, only the hydrophobic IpaB and IpaC were tightly associated with RBC membranes isolated after hemolysis. Ipa protein secretion and hemolysis were kinetically coupled processes. However, Ipa protein secretion in the immediate vicinity of RBCs was not sufficient to cause hemolysis in the absence of centrifugation. Centrifugation reduced the distance between bacterial and RBC membranes beyond a critical threshold. Electron microscopy analysis indicated that secretons were constitutively assembled at 37°C before any host contact. They were composed of three parts: (a) an external needle, (b) a neck domain, and (c) a large proximal bulb. Secreton morphology did not change upon activation of secretion. In mutants of some genes encoding the secretion machinery the organelle was absent, whereas ipaB and ipaC mutants displayed normal secretons.