Department of Biochemistry and Centre de recherche en biologie structurale, McGill University, Montreal, Quebec, Canada.
Department of Biochemistry and Centre de recherche en biologie structurale, McGill University, Montreal, Quebec, Canada.
J Biol Chem. 2022 Jul;298(7):102114. doi: 10.1016/j.jbc.2022.102114. Epub 2022 Jun 8.
Parkin and PINK1 regulate a mitochondrial quality control system that is mutated in some early onset forms of Parkinson's disease. Parkin is an E3 ubiquitin ligase and regulated by the mitochondrial kinase PINK1 via a two-step cascade. PINK1 first phosphorylates ubiquitin, which binds a recruitment site on parkin to localize parkin to damaged mitochondria. In the second step, PINK1 phosphorylates parkin on its ubiquitin-like domain (Ubl), which binds a regulatory site to release ubiquitin ligase activity. Recently, an alternative feed-forward mechanism was identified that bypasses the need for parkin phosphorylation through the binding of a second phosphoubiquitin (pUb) molecule. Here, we report the structure of parkin activated through this feed-forward mechanism. The crystal structure of parkin with pUb bound to both the recruitment and regulatory sites reveals the molecular basis for differences in specificity and affinity of the two sites. We use isothermal titration calorimetry measurements to reveal cooperativity between the two binding sites and the role of linker residues for pUbl binding to the regulatory site. The observation of flexibility in the process of parkin activation offers hope for the future design of small molecules for the treatment of Parkinson's disease.
Parkin 和 PINK1 调节一个线粒体质量控制系统，该系统在一些早发性帕金森病的形式中发生突变。Parkin 是一种 E3 泛素连接酶，通过两步级联反应被线粒体激酶 PINK1 调节。PINK1 首先磷酸化泛素，泛素结合 parkin 上的募集位点将 parkin 定位到受损的线粒体。在第二步中，PINK1 在 parkin 的泛素样结构域（Ubl）上磷酸化 parkin，这结合了一个调节位点以释放泛素连接酶活性。最近，发现了一种替代的前馈机制，通过结合第二个磷酸泛素（pUb）分子，绕过了 parkin 磷酸化的需要。在这里，我们报告了通过这种前馈机制激活的 parkin 的结构。与招募和调节位点结合的 pUb 结合的 parkin 的晶体结构揭示了两个位点特异性和亲和力差异的分子基础。我们使用等温滴定量热法测量来揭示两个结合位点之间的协同作用以及连接残基在 pUbl 结合到调节位点中的作用。在 parkin 激活过程中观察到的灵活性为未来治疗帕金森病的小分子设计提供了希望。
