Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Université de la Méditerranée - Aix-Marseille II, CNRS - UPR 9027, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
Mol Microbiol. 2010 Feb;75(4):886-99. doi: 10.1111/j.1365-2958.2009.07028.x.
Type VI secretion systems (T6SS) are multi-component machines encoded within the genomes of most Gram-negative bacteria that associate with plant, animal and/or human cells, and therefore are considered as potential virulence factors. We recently launched a study on the Sci-1 T6SS of enteroaggregative Escherichia coli (EAEC). The Sci-1 T6SS is composed of all or a subset of the 21 gene products encoded within the cluster, 13 of which are shared by all T6SS identified so far. In the present work, we focussed our attention on the SciZ protein. We first showed that SciZ is required for the release of the Hcp protein in the culture supernatant and for efficient biofilm formation, demonstrating that SciZ is necessary for EAEC T6SS function. Indeed, SciZ forms a complex with SciP, SciS and SciN, three core components of the transport apparatus. Fractionation and topology studies showed that SciZ is a polytopic inner membrane protein with three trans-membrane segments. Computer analyses identified a motif shared by peptidoglycan binding proteins of the OmpA family in the SciZ periplasmic domain. Using in vivo and in vitro binding assays, we showed that this motif anchors the SciZ protein to the cell wall and is required for T6SS function.
VI 型分泌系统（T6SS）是大多数革兰氏阴性菌基因组中编码的多组分机器，与植物、动物和/或人类细胞有关，因此被认为是潜在的毒力因子。我们最近启动了一项关于肠聚集性大肠杆菌（EAEC）Sci-1 T6SS 的研究。Sci-1 T6SS 由该簇内编码的 21 个基因产物的全部或子集组成，其中 13 个是迄今为止鉴定的所有 T6SS 所共有的。在本工作中，我们将注意力集中在 SciZ 蛋白上。我们首先表明，SciZ 是 Hcp 蛋白在培养上清液中释放和有效生物膜形成所必需的，这表明 SciZ 是 EAEC T6SS 功能所必需的。事实上，SciZ 与 SciP、SciS 和 SciN 形成复合物，这三种蛋白是输送装置的核心组件。分级和拓扑研究表明，SciZ 是一种具有三个跨膜片段的多跨膜内膜蛋白。计算机分析鉴定出 SciZ 周质域中与 OmpA 家族肽聚糖结合蛋白共享的基序。通过体内和体外结合实验，我们表明该基序将 SciZ 蛋白锚定在细胞壁上，并且是 T6SS 功能所必需的。
