Ge Jinghua, Bian Xin, Ma Lu, Cai Yiying, Li Yanghui, Yang Jie, Karatekin Erdem, De Camilli Pietro, Zhang Yongli
Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.
Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA.
Nat Chem Biol. 2022 Mar;18(3):313-320. doi: 10.1038/s41589-021-00914-3. Epub 2021 Dec 16.
Extended synaptotagmins (E-Syts) mediate lipid exchange between the endoplasmic reticulum (ER) and the plasma membrane (PM). Anchored on the ER, E-Syts bind the PM via an array of C2 domains in a Ca- and lipid-dependent manner, drawing the two membranes close to facilitate lipid exchange. How these C2 domains bind the PM and regulate the ER-PM distance is not well understood. Here, we applied optical tweezers to dissect PM binding by E-Syt1 and E-Syt2. We detected Ca- and lipid-dependent membrane-binding kinetics of both E-Syts and determined the binding energies and rates of individual C2 domains or pairs. We incorporated these parameters in a theoretical model to recapitulate salient features of E-Syt-mediated membrane contacts observed in vivo, including their equilibrium distances and probabilities. Our methods can be applied to study other proteins containing multiple membrane-binding domains linked by disordered polypeptides.
延伸突触结合蛋白（E-Syts）介导内质网（ER）与质膜（PM）之间的脂质交换。E-Syts锚定在内质网上，通过一系列C2结构域以钙和脂质依赖的方式结合质膜，使两个膜靠近以促进脂质交换。这些C2结构域如何结合质膜并调节内质网-质膜距离尚不清楚。在这里，我们应用光镊来剖析E-Syt1和E-Syt2与质膜的结合。我们检测了两种E-Syts的钙和脂质依赖的膜结合动力学，并确定了单个C2结构域或结构域对的结合能和结合速率。我们将这些参数纳入一个理论模型，以概括在体内观察到的E-Syt介导的膜接触的显著特征，包括它们的平衡距离和概率。我们的方法可应用于研究其他含有由无序多肽连接的多个膜结合结构域的蛋白质。
