Structure of signal peptide peptidase

描述（由申请人提供）：多蛋白复合物γ -分泌酶蛋白水解地切割淀粉样前体蛋白（APP）的膜内区域，从而形成阿尔茨海默病（AD）患者中发现的斑块。分泌酶的催化成分是称为早老素的膜内天冬氨酸蛋白酶（IAP）。早老素突变与家族性早发性AD直接相关。IAP家族的另一个已知成员是信号肽肽酶（signal peptide peptide ase， SPP），它的作用是在被信号肽酶切割后对残馀的信号肽进行进一步的蛋白水解。对单个spp的生物化学和功能的了解才刚刚开始被阐明，而且在所有生命领域都发现了同源物。早老素和SPP表现出显著的序列相似性，强烈表明它们具有相同的结构和催化特征。因此，对更易处理的SPP的分子理解可能会影响早老素和分泌酶的药物设计。本提案的目标是通过过渡态模拟抑制剂和底物模拟物来表达，表征和解决嗜极细菌SPP同源物本身的晶体结构。此外，候选药物将在计算机上进行筛选。这种膜内蛋白酶的第一个结构将为膜内蛋白水解的生物化学提供关键的见解，并使基于结构的AD药物开发和筛选成为可能。

DESCRIPTION (provided by applicant): The multiprotein complex gamma-secretase proteolytically cleaves the intramembrane region of amyloid precursor protein (APP), which in turn forms the plaques found in Alzheimer's disease (AD) patients. The catalytic component of gamma-secretase is the intramembrane aspartyl protease (IAP) called presenilin. Mutations in presenilin are directly linked to familial early-onset AD. Another known member of the IAP family is signal peptide peptidase (SPP), which functions to further proteolyze remnant signal peptides after they have been cleaved by signal peptidase. Knowledge of the biochemistry and function of individual SPPs are only beginning to be elucidated, and homologues are found in all kingdoms of life. Presenilin and SPP exhibit significant sequence similarity, strongly suggesting they share structural and catalytic features. Thus, a molecular understanding of the more tractable SPP will likely impact drug design for presenilin and gamma- secretase. The goal of this proposal is to express, characterize, and solve the crystal structure of an extremophilic bacterial SPP ortholog by itself, with a transition-state analog inhibitor and with a substrate mimic. In addition, drug candidates will be screened in silico. This first structure of an intramembrane protease will provide critical insight into the biochemistry of intramembrane proteolysis and enable structure- based AD drug development and screening.