Extended Data Fig. 7: Mutually exclusive interactions of the EMC holdase and CaVα2δ with the core CaV1.2/CaVβ3 complex and ordering of the CaV1.2 pore and VSDs by CaVα2δ.
From: EMC chaperone–CaV structure reveals an ion channel assembly intermediate
a, Superposition of CaVα2δ-1 (semi-transparent, aquamarine) from the CaV1.2(ΔC)/CaVβ3/CaVα2δ-1 structure with the EMC:CaV1.2/CaVβ3 complex. EMC1 surface is shown. Red oval highlights clash regions. Colours of the EMC:CaV1.2/CaVβ3 complex are as in Fig. 1a. Grey bars denote the membrane. b, Close up view of clash between EMC1 (light blue) and CaVα2δ-1 (aquamarine). EMC1, EMC3 (magenta), EMC5 (pink), EMC6 (white), VSD I (yellow orange), PD II (firebrick), and PD III (lime) from the EMC:CaV1.2/CaVβ3 complex are shown. Red oval highlights clash regions. CaVα2δ-1 domains are indicated. Divalent staple is indicated. SF calcium ions are from CaV1.2(ΔC)/CaVβ3/CaVα2δ-1 and mark the location of the pore in the CaVα2δ-assembled channel. c, Superposition of VSD I (yellow orange), PD II (firebrick), and PD III (lime) from the EMC complex (semi-transparent) and their corresponding parts from CaV1.2(ΔC)/CaVβ3/CaVα2δ-1 (slate). CaVα2δ-1 (aquamarine) is shown as a semi-transparent surface. Calcium ions are from CaV1.2(ΔC)/CaVβ3/CaVα2δ-1. Left inset shows the coordination of the divalent staple by the VWA domain MIDAS and D151 in CaV1.2(ΔC)/CaVβ3/CaVα2δ-1. Red distance shows the position of CaV1.2 D151 in the EMC complex relative to the calcium ion in the CaVα2δ complex. Asterisks mark positions where coordinated alanine mutation impair the ability of CaVα2δ to enhance CaV currents and surface expression59. Right inset shows the extensive contacts between PD II and PD III loops with CaVα2δ in the CaV1.2(ΔC)/CaVβ3/CaVα2δ-1 complex. The PD III loops are disordered in the EMC:CaV1.2/CaVβ3 complex. CaVα2δ-1 residues are in italics. d, Schematic showing of the conformational changes and interaction sites in the exchange between the EMC:CaV/CaVβ holdase complex and assembled CaV/CaVβ/CaVα2δ channel. Black ovals indicate key interaction sites in each complex.
