Organization and Function of a Type II Secretion Complex

描述（由申请人提供）：II型分泌途径广泛存在于 分布在革兰氏阴性病原体中， 毒素和降解酶的细胞外分泌。至少12个基因 位于细胞质和外膜上的产物 包括II型分泌器， 分泌的蛋白质从周质转移到细胞外 环境。这一途径具有高度特异性。它区分分泌蛋白质 从常驻周质蛋白质，并区分其自身分泌 蛋白质和从密切相关的物种引入的蛋白质。此外，本发明还提供了一种方法， 通过这种途径的分泌不同于大多数其他膜转运 系统，因为其底物由折叠蛋白质组成。 本提案的目的是说明第二类机制的特点 在分子水平上的分泌。这些研究将利用霍乱弧菌， 将专门检查霍乱毒素（CT）的分泌，以及其他 利用II型途径的蛋白质。CT提供了一个很好的模型 由于蛋白质的结构和功能以及 折叠和组装途径被很好地表征。具体来说，我们将 检验以下假设：1）II型系统分泌的分子编码 在它们的三级结构中对它们的分泌至关重要的信息，2） II型复合体跨越膜和参与连接膜的组件。 外膜分泌孔与细胞质膜调节分泌 通过将能量转换到分泌孔或通过调节其开口，3） 分泌器定位于极或隔膜， 肽聚糖经历重排和/或其中孔径是非典型的 以允许分泌折叠的蛋白质。

DESCRIPTION (provided by applicant): The type II secretion pathway is widely distributed among Gram-negative pathogens where it is responsible for extracellular secretion of toxins and degradative enzymes. At least 12 gene products located in both the cytoplasmic and outer membrane collectively comprise the type II secretion apparatus, which is specifically required for the translocation of secreted proteins from the periplasm to the extracellular milieu. This pathway is highly specific. It distinguishes secreted proteins from resident periplasmic proteins and discriminates between its own secreted proteins and those introduced from closely related species. In addition, secretion through this pathway differs from most other membrane transport systems in that its substrates consist of folded proteins. The objective of this proposal is to characterize the mechanism of type II secretion at the molecular level. The studies will utilize Vibrio cholerae and will specifically examine the secretion of cholera toxin (CT), as well as other proteins that utilize the type II pathway. CT provides an excellent model protein for these studies since its structure and function as well as its folding and assembly pathway are very well characterized. Specifically, we will test the hypotheses that: 1) Molecules secreted by the type II system encode information critical to their secretion within their tertiary structure, 2) the type II complex spans both membranes and components involved in connecting the outer membrane secretion pore with the cytoplasmic membrane regulate secretion by transducing energy to the secretion pore or by regulating its opening, 3) the secretion apparatus is localized to the poles or septum where the peptidoglycan undergoes rearrangements and/or where the pore size is atypical to allow for secretion of folded proteins.