Voltage-gated ion channels (VGICs) comprise multiple structural units whose assembly is required for function^1,2. There is scant structural understanding of how VGIC subunits assemble and whether chaperone proteins are required. High-voltage activated calcium channels (Ca_Vs)^3,4 are paradigmatic multi-subunit VGICs whose function and trafficking is powerfully shaped by interactions between pore-forming Ca_V1 or Ca_V2 Ca_Vα₁³ and auxiliary Ca_Vβ⁵, and Ca_Vα₂δ subunits^6,7. Here, we present cryo-EM structures of human brain and cardiac Ca_V1.2 bound with Ca_Vβ₃ to a chaperone, the endoplasmic reticulum membrane protein complex (EMC)^8,9, and of the assembled Ca_V1.2/Ca_Vβ₃/Ca_Vα₂δ-1 channel. These provide a view of an EMC:client complex and define EMC sites, the TM and Cyto docks, whose interaction with the client channel causes partial extraction of a pore subunit and splays open the Ca_Vα₂δ interaction site. The structures identify the Ca_Vα₂δ binding site for gabapentinoid anti-pain and anti-anxiety drugs⁶, show that EMC and Ca_Vα₂δ channel interactions are mutually exclusive, and indicate that EMC to Ca_Vα₂δ handoff involves a divalent ion-dependent step and Ca_V1.2 element ordering. Disruption of the EMC:Ca_V complex compromises Ca_V function suggesting that the EMC acts as a channel holdase that facilitates channel assembly. Together, the structures unveil a Ca_V assembly intermediate and EMC client binding sites, with potentially wide-reading implications for biogenesis of VGICs and other membrane proteins.

电压门控离子通道 (VGIC) 包含多个结构单元，其组装是功能^1,2所必需的。对于 VGIC 亚基如何组装以及是否需要伴侣蛋白，人们在结构上了解甚少。高压激活钙通道 (Ca _V s) ^3,4是典型的多亚基 VGIC，其功能和运输受到成孔 Ca _V 1 或 Ca _V 2 Ca _V α ₁ ³和辅助 Ca _V β 之间相互作用的强烈影响。 ⁵和Ca _V α ₂ δ 亚基^6,7 。在这里，我们展示了人脑和心脏 Ca _V 1.2 与 Ca _V β ₃结合到伴侣、内质网膜蛋白复合物 (EMC) ^8,9以及组装的 Ca _V 1.2/Ca _V β 的冷冻电镜结构。 ₃ /Ca _V α ₂ δ-1 通道。这些提供了 EMC:client 复合物的视图，并定义了 EMC 位点、TM 和 Cyto 码头，它们与 client 通道的相互作用导致孔亚基的部分提取，并张开 Ca _V α ₂ δ 相互作用位点。该结构确定了加巴喷丁类抗疼痛和抗焦虑药物的 Ca _V α ₂ δ 结合位点⁶ ，表明 EMC 和 Ca _V α ₂ δ 通道相互作用是相互排斥的，并表明 EMC 到 Ca _V α ₂ δ 的切换涉及二价离子依赖性步骤和 Ca _V 1.2 元素排序。 EMC:Ca _V复合物的破坏会损害 Ca _V功能，表明 EMC 充当通道保持酶，促进通道组装。这些结构共同揭示了 Ca _V组装中间体和 EMC 客户结合位点，对 VGIC 和其他膜蛋白的生物发生具有潜在的广泛意义。