Immunology Program and Medical Scientist Training Program, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Internal Medicine, Division of Pulmonary and Critical Care, Washington University School of Medicine, St. Louis, MO 63110, USA.
Department of Internal Medicine, Division of Pulmonary and Critical Care, Washington University School of Medicine, St. Louis, MO 63110, USA; Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
Cell Rep. 2020 Jan 28;30(4):1141-1151.e3. doi: 10.1016/j.celrep.2019.12.059.
The secreted protein calcium-activated chloride channel regulator 1 (CLCA1) utilizes a von Willebrand factor type A (VWA) domain to bind to and potentiate the calcium-activated chloride channel TMEM16A. To gain insight into this unique potentiation mechanism, we determined the 2.0-Å crystal structure of human CLCA1 VWA bound to Ca. The structure reveals the metal-ion-dependent adhesion site (MIDAS) in a high-affinity "open" conformation, engaging in crystal contacts that likely mimic how CLCA1 engages TMEM16A. The CLCA1 VWA contains a disulfide bond between α3 and α4 in close proximity to the MIDAS that is invariant in the CLCA family and unique in VWA structures. Further biophysical studies indicate that CLCA1 VWA is preferably stabilized by Mg over Ca and that α6 atypically extends from the VWA core. Finally, an analysis of TMEM16A structures suggests residues likely to mediate interaction with CLCA1 VWA.
分泌蛋白钙激活氯离子通道调节剂 1（CLCA1）利用血管性血友病因子 A 型（VWA）结构域与钙激活氯离子通道 TMEM16A 结合并增强其功能。为了深入了解这种独特的增强机制，我们测定了与人 CLCA1 VWA 结合 Ca 的 2.0-Å 晶体结构。该结构揭示了金属离子依赖性粘附位点（MIDAS）处于高亲和力“开放”构象，与晶体接触，可能模拟 CLCA1 与 TMEM16A 的结合方式。CLCA1 VWA 在 MIDAS 附近包含α3 和α4 之间的二硫键，该二硫键在 CLCA 家族中是不变的，在 VWA 结构中是独特的。进一步的生物物理研究表明，CLCA1 VWA 更喜欢被 Mg 而不是 Ca 稳定，并且α6 异常地从 VWA 核心延伸出来。最后，对 TMEM16A 结构的分析表明，可能存在与 CLCA1 VWA 相互作用的残基。
