Molecular Mechanism of Pathogenesis

描述（由申请人提供）：耶尔森菌效应物YopT和假单胞菌无毒蛋白AvrPphB定义了一个涉及细菌发病机制的19个蛋白家族。我们发现YopT和AvrPphB都是半胱氨酸蛋白酶，它们的蛋白水解活性依赖于整个YopT家族中保守的不变C/HID残基。YopT在翻译后修饰的Rho gtpase的羧基末端附近切割，将它们从膜上释放出来。这导致宿主细胞中肌动蛋白细胞骨架的破坏。AvrPphB的蛋白水解活性对于AvrPphB前体的自蛋白水解裂解以及在植物中引发超敏反应至关重要。大多数无毒蛋白（Avr）的生化功能尚不清楚。该提案的重点是发展AvrPphB蛋白家族如何被激活和翻译后修饰的分子理解。此外，还描述了鉴定AvrPphB底物的努力。最后，我们提出获得AvrPphB与肽底物络合的x射线结构。这些实验将为我们对发病机理的分子机制提供新的认识。

DESCRIPTION (provided by applicant): A Yersinia effector known as YopT and a Pseudomonas avirulence protein known as AvrPphB define a family of 19 proteins involved in bacterial pathogenesis. We show that both YopT and AvrPphB are cysteine proteases, and their proteolytic activities are dependent upon the invariant C/HID residues conserved in the entire YopT family. YopT cleaves the post-translationally modified Rho GTPases near their carboxyl termini, releasing them from the membrane. This leads to the disruption of actin cytoskeleton in host cells. The proteolytic activity of AvrPphB is essential for autoproteolytic cleavage of an AvrPphB precursor as well as for eliciting the hypersensitive response in plants. The biochemical functions of most avirulence (Avr) proteins are unknown. This proposal focuses on developing a molecular understanding of how the AvrPphB family of proteins is activated and post-translationally modified. In addition, efforts to identify the substrate(s) for AvrPphB are described. Finally, we propose to obtain the x-ray structure of AvrPphB complexed with a peptide substrate. These experiments will provide us with new insights into the molecular mechanism of pathogenesis.