Fig. 1: Overall structure of the auto-inhibited RDGC/CaM holoenzyme in the absence of Ca²⁺.

a Schematic representation of the domain organization of RDGC. Dro, Drosophila. b Cryogenic-electron microscopy (Cryo-EM) density map of the RDGC/CaM holoenzyme in the absence of Ca²⁺. Unless otherwise indicated, individual domains are displayed in distinct colors throughout the manuscript, as follows: CaM, dark orange; extended-IQ motif, lime green; catalytic domain, medium purple; EF-like domain, Indian red; and EF-hand domain, dodger blue. The map contour level is 0.16. c Schematic representation of the RDGC/CaM holoenzyme in the absence of Ca²⁺. A close-up view of the catalytic domain, encompassing the extended-IQ motif, EF-like domain, EF-hand domain, and CaM, is shown. The catalytic sites are labeled. d Atomic model and cryo-EM densities of the RDGC catalytic domain and catalytic sites, with metal ions 1 (M1) and 2 (M2) shown as spheres. The map contour level is 0.214. e Extended-IQ motif of RDGC, with side chains displayed as sticks within the cryo-EM densities. The map contour level is 0.1. f Cryo-EM densities and atom representation for the EF-like domain and EF-hand domain of RDGC. The map contour level is 0.13. g Electron density covering the CaM atomic model. Superposition of CaM from the cryo-EM structure (PDB ID: 8JFW) onto the isolated Ca²⁺-free CaM N and C lobes from the crystal structure (PDB ID: 8ZLX) is shown. Ca²⁺-binding pockets are shown in the EM-density maps. The map contour level is 0.1.