Université de Lyon, F-69003, Université Lyon 1, Lyon, F-69622, INSA-Lyon, Villeurbanne, F-69621, CNRS, UMR5240, Microbiologie Adaptation et Pathogénie, Lyon, F-69622, France.
Mol Microbiol. 2010 May;76(4):944-55. doi: 10.1111/j.1365-2958.2010.07149.x. Epub 2010 Apr 1.
The type II secretion system (T2SS) is widely exploited by proteobacteria to secrete enzymes and toxins involved in bacterial survival and pathogenesis. The outer membrane pore formed by the secretin OutD and the inner membrane protein OutC are two key components of the secretion complex, involved in secretion specificity. Here, we show that the periplasmic regions of OutC and OutD interact directly and map the interaction site of OutC to a 20-residue peptide named OutCsip (secretin interacting peptide, residues 139-158). This peptide interacts in vitro with two distinct sites of the periplasmic region of OutD, one located on the N0 subdomain and another overlapping the N2-N3' subdomains. The two interaction sites of OutD have different modes of binding to OutCsip. A single substitution, V143S, located within OutCsip prevents its interaction with one of the two binding sites of OutD and fully inactivates the T2SS. We show that the N0 subdomain of OutD interacts also with a second binding site within OutC located in the region proximal to the transmembrane segment. We suggest that successive interactions between these distinct regions of OutC and OutD may have functional importance in switching the secretion machine.
II 型分泌系统（T2SS）被广泛应用于变形菌来分泌与细菌存活和发病机制相关的酶和毒素。由分泌蛋白 OutD 和内膜蛋白 OutC 形成的外膜孔是分泌复合物的两个关键组成部分，参与了分泌的特异性。在这里，我们发现 OutC 和 OutD 的周质区域直接相互作用，并确定了 OutC 的相互作用位点位于一个 20 个残基的肽上，命名为 OutCsip（分泌蛋白相互作用肽，残基 139-158）。该肽在体外与 OutD 的周质区域的两个不同位点相互作用，一个位于 N0 亚结构域，另一个与 N2-N3' 亚结构域重叠。OutD 的两个相互作用位点与 OutCsip 的结合方式不同。位于 OutCsip 内的单个取代 V143S 阻止了其与 OutD 的两个结合位点之一的相互作用，并使 T2SS 完全失活。我们表明，OutD 的 N0 亚结构域还与 OutC 内的第二个结合位点相互作用，该位点位于跨膜片段附近的区域。我们认为，OutC 和 OutD 的这些不同区域之间的连续相互作用可能对切换分泌机器具有功能重要性。
