Conformational states and recognition of amyloidogenic peptides of human insulin-degrading enzyme
Conformational states and recognition of amyloidogenic peptides of human insulin-degrading enzyme
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DOI：
10.1073/pnas.1304575110
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发表时间：
2013-08-20
影响因子：
11.1
通讯作者：
Tang, Wei-Jen
中科院分区：
文献类型：
--
作者：
McCord, Lauren A.;Liang, Wenguang G.;Tang, Wei-Jen
胰岛素降解酶（IDE）选择性地降解淀粉样蛋白肽单体，并有助于清除淀粉样蛋白（A β）。因此，IDE延缓了阿尔茨海默病的进展。IDE具有一个封闭的催化室，吞没和降解其肽底物；然而，IDE功能的分子机制，包括底物进入腔室和识别，仍然是难以捉摸的。在这里，我们通过使用合成抗体片段作为结晶伴侣捕获了独特的IDE构象。门子域的意外位移产生了一个类似于18埃的腔室开口。这种旋转门机制允许短肽进入催化室并破坏IDE门亚域内的催化位点。鉴于淀粉样蛋白肽倾向于转化为β -链以聚合成淀粉样原纤维，它们也使用β -链来稳定位于IDE门亚域的被破坏的催化位点，以便被IDE降解。因此，摇摆门的作用允许IDE通过底物诱导的IDE催化裂口的稳定来识别淀粉样变性。小角x射线散射（SAXS）分析表明，IDE以闭合态和开放态混合存在。这些开放状态，不同于旋转门状态，允许较大的底物（例如，A β，胰岛素）进入腔室，并且在溶液中是优选的。突变研究证实了门亚结构域和连接IDE的N端和c端半部分的铰链环在催化中的关键作用。总之，我们的数据提供了IDE的构象变化的见解，控制淀粉样蛋白肽的选择性破坏。
Insulin-degrading enzyme (IDE) selectively degrades the monomer of amyloidogenic peptides and contributes to clearance of amyloid beta (A beta). Thus, IDE retards the progression of Alzheimer's disease. IDE possesses an enclosed catalytic chamber that engulfs and degrades its peptide substrates; however, the molecular mechanism of IDE function, including substrate access to the chamber and recognition, remains elusive. Here, we captured a unique IDE conformation by using a synthetic antibody fragment as a crystallization chaperone. An unexpected displacement of a door subdomain creates an similar to 18-angstrom opening to the chamber. This swinging-door mechanism permits the entry of short peptides into the catalytic chamber and disrupts the catalytic site within IDE door subdomain. Given the propensity of amyloidogenic peptides to convert into beta-strands for their polymerization into amyloid fibrils, they also use such beta-strands to stabilize the disrupted catalytic site resided at IDE door subdomain for their degradation by IDE. Thus, action of the swinging door allows IDE to recognize amyloidogenicity by substrate-induced stabilization of the IDE catalytic cleft. Small angle X-ray scattering (SAXS) analysis revealed that IDE exists as a mixture of closed and open states. These open states, which are distinct from the swinging door state, permit entry of larger substrates (e. g., A beta, insulin) to the chamber and are preferred in solution. Mutational studies confirmed the critical roles of the door subdomain and hinge loop joining the N- and C-terminal halves of IDE for catalysis. Together, our data provide insights into the conformational changes of IDE that govern the selective destruction of amyloidogenic peptides.