Organization and Function of a Type II Secretion Complex

描述(申请人提供)：II型分泌途径广泛存在 在革兰氏阴性病原体中分布，在那里它负责 毒素和降解酶的胞外分泌。至少12个基因 产物同时位于细胞质和外膜上。 包括II型分泌器，该分泌器专门用于 将分泌的蛋白质从周质转移到细胞外 周围的环境。这条途径具有很高的特异性。它能区分分泌的蛋白质 从驻留的周质蛋白中分离出来并区分其自身分泌的 蛋白质和那些从近亲物种引进的蛋白质。此外, 通过这一途径进行的分泌与大多数其他膜运输不同。 其底物由折叠的蛋白质组成的系统。 这项建议的目标是描述第二类的机制。 在分子水平上的分泌。这些研究将利用霍乱弧菌和 将专门检查霍乱毒素(CT)的分泌情况，以及其他 利用第二类途径的蛋白质。CT提供了一个很好的模式 用于这些研究的蛋白质的结构和功能以及其 折叠和组装途径得到了很好的描述。具体来说，我们将 检验以下假设：1)由类型II系统分泌的分子编码 在它们的三级结构中对其分泌至关重要的信息，2) 第二类复合体跨越膜和组件，涉及连接 外膜分泌孔与胞质膜调节分泌 通过向分泌孔传递能量或通过调节分泌孔的开度，3) 分泌器位于极部或隔部，其中 肽聚糖经历重排和/或孔大小不典型 以允许折叠蛋白质的分泌。

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.