Figure 4.

Structure of Munc13‐1. (A) Domain diagram of Munc13‐1. The calmodulin‐binding sequence is labeled CaMb. The number on the right above the diagram indicates the length of the protein. (B–G) Ribbon diagrams of the three‐dimensional structures of the C₁ domain110 (B), the Ca²⁺‐bound C₂B domain111 (C) and the C₁C₂BMUN fragment48 (D) of Munc13‐1, as well as calmodulin (purple) bound to the Munc13‐1 CaMb sequence (red)114 (E), the Munc13‐1 C₂A domain homodimer116 (F) and the heterodimer of the Munc13‐1 C₂A domain (orange) with the RIM2α ZF domain (blue)116 (G). The PDB accession codes are 1Y8F, 3KWU, 5UE8, 2KDU, 2CJT and 2CJS, respectively. Ca²⁺ ions are shown as purple spheres and zinc ions are shown as yellow spheres. In (D), the locations of the DAG/phorbol ester‐binding site in the C₁ domain, the Ca²⁺/PIP₂‐binding site in the C₂B domain, and a polybasic region formed by the C₁ domain, the C₂B domain and the linker sequence between them are indicated.