MINORITY PREDOCTORAL FELLOWSHIP PROGRAM

病原生物必须完成几个任务才能引起疾病，包括毒力因子的分泌。然而，革兰氏阴性菌有两层膜，中间有一个空间，这对分泌造成了巨大的障碍。自动转运蛋白（ATs）是一类蛋白质，其特征是在n端有一个信号序列，引导它们进入质周空间，在外膜形成一个桶状结构域的c端结构域，以及通过这个桶转运的乘客结构域，它们为这个问题提供了一个非常简单的解决方案。然而，ATs的外膜易位尚不清楚。汽车运输车可进一步分为亚科。其中之一是肠杆菌科丝氨酸蛋白酶自转运体（SPATES）。这些是分泌的毒力因子，在其乘客域具有丝氨酸蛋白酶基序。本提案旨在研究该亚家族成员EspP的分泌机制，作为SPATES的模型。我们的假设是，EspP将有一个连接区域，有助于通过外膜的乘客域的有效易位。第一个目标是确定该连接体的预期二级结构。第二个目的是研究有效外膜易位和c端插入外膜的连接子结构与功能之间的关系。这些研究将有助于实现了解自身转运蛋白分泌的长期目标，从而开发其用于活疫苗抗原呈递的潜在用途。它们还将提供对革兰氏阴性发病机制的更清晰理解。

Pathogenic organisms must accomplish several tasks in order to cause disease, including the secretion of virulence factors. Gram-negative bacteria, however, have two membranes and a space in between that creates a formidable obstacle to secretion. The autotransporters (ATs), a family of proteins characterized by a signal sequence at the N-terminus that directs them to the periplasmic space, a C-terminal domain that forms a barrel in the outer membrane, and a passenger domain that is translocated through this barrel, provide a remarkably simple solution for this problem. However, outer membrane translocation by ATs is not well understood. The autotransporters can be further divided into subfamilies. One of these is the Serine Protease Autotransporters of Enterobacteriaceae (SPATES). These are secreted virulence factors that possess a serine protease motif in their passenger domains. This proposal seeks to study the mechanism of secretion of EspP, a member of this subfamily, as a model for the SPATES. Our hypothesis is that EspP will have a linker region that aids in efficient translocation of the passenger domain through the outer membrane. The first aim seeks to define the predicted secondary structure of this linker. The second aim is to study the relationship between linker structure and function both for efficient outer membrane translocation and insertion of the C-terminus into the outer membrane. These studies will help in accomplishing the long-term goals of understanding autotransporter secretion so that its potential use for antigen presentation in live vaccines can be developed. They will also provide a clearer understanding of gram-negative pathogenesis.