Analysis of membrane-associated components of the type III secretion system from Xanthomonas campestris pv. vesicatoria

植物病原细菌野油菜黄单胞菌致病变种（Xanthomonascampestrispv.）水疱病利用III型分泌（T3 S）系统将效应蛋白直接易位到宿主细胞胞质溶胶中。跨膜分泌器由11个保守组分和几个非保守组分组成。在这个项目中，我们将进行体外和体内蛋白质-蛋白质相互作用的研究与预测的T3 S系统的内膜和外膜组件，以获得第一次深入了解这种分子纳米机器的组装。此外，我们将测试内膜相关成分和分泌蛋白之间可能的相互作用，以确定T3 S系统的底物对接位点。我们的研究结果的生物学意义将通过遗传学方法来解决。我们还旨在鉴定内膜蛋白HrcU的胞质区域中的功能残基，其参与T3 S底物特异性的控制。HrcU属于在动物病原菌中研究的FlhB/YscU蛋白家族。值得注意的是，我们最近的实验揭示了动物病原体中FlhB/YscU介导的底物特异性开关的机制的显着差异。因此，T3 S系统的控制机制可能在不同病原体之间存在显著差异。

The plant pathogenic bacterium Xanthomonas campestris pv. vesicatoria employs a type III secretion (T3S) system to translocate effector proteins directly into the host cell cytosol. The membrane-spanning secretion apparatus consists of eleven conserved and several non-conserved components. In this project, we will perform in vitro and in vivo protein-protein interaction studies with predicted inner and outer membrane components of the T3S system to gain first insights into the assembly of this molecular nanomachine. Furthermore, we will test possible interactions between inner membrane-associated components and secreted proteins to identify substrate docking sites of the T3S system. The biological significance of our findings will be addressed by genetic approaches. We also aim at the identification of functional residues in the cytoplasmic region of the inner membrane protein HrcU, which is involved in the control of T3S substrate specificity. HrcU belongs to the FlhB/YscU protein family that was studied in animal pathogenic bacteria. Notably, our recent experiments revealed striking differences to the mechanisms proposed for the FlhB/YscU-mediated substrate specificity switch in animal pathogens. It is therefore likely that control mechanisms of T3S systems vary significantly among different pathogens.