Figure 2. Cryo-EM maps and models of full-length CaSR.

(A) Left panel shows the view of CaSR in the active conformation (purple) from front view, and the right panel shows the view after a 90° rotation as indicated. (B) Left panel shows the view of CaSR in the inactive conformation (cyan) bound to NB-2D11 (orange) from front view, and the right panel shows the view after a 90° rotation as indicated. (C) Model (Ribbon representation) of CaSR shows the structure of the active state (purple) bound to TNCA (red) and Ca²⁺ ion (green) viewed from the side. (D) Model (Ribbon representation) of CaSR shows the structure of the inactive state (cyan) bind with NB-2D11 (orange).

Figure 2—figure supplement 1. Cryo-EM processing workflow of CaSR bound to agonist+PAM.

(A) The flow chart displaying the cryo-EM processing of agonist+PAM bound CaSR in GDN. (B) Cryo-EM class averages of agonist+PAM bound CaSR in GDN micelles. (C) Local resolution map of agonist+PAM bound CaSR. (D) Gold standard Fourier shell correlation (FSC) curve indicates that the map for agonist+PAM bound CaSR reaches nominal resolutions of 2.99 Å at FSC = 0.143. (E) Particle angular distribution of the final cryo-EM reconstruction of agonist+PAM bound CaSR.

Figure 2—figure supplement 2. Agreement between the cryo-EM map of CaSR bound to agonist+PAM and the model.

(A) The cryo-EM densities and fitted atomic models of B and C helices of CaSR in agonist+PAM bound conformation. (B) The cryo-EM densities and fitted atomic models of TNCA and related amino acids.

Figure 2—figure supplement 3. Cryo-EM maps and models of CaSR.

(A, B) The full-length CaSR cryo-EM maps and models present view from front view in the agonist+ PAM bound state (purple) (A), and the fully inactive state (cyan) with deletion of NB-2D11 for clarity (B). Positions in the VFT (red, E228), CRD (green, E558), CRD/7TMD interface (blue, T609), and 7TM domain (yellow, P823) show that the active state is characterized by smaller intersubunit distances. The P823 position in the active model (yellow) shows the contact of 7TMDs. (C, D) Comparison of the intersubunit interfaces in active and inactive CaSR are shown for active (C) and inactive (D) CaSR. Contact regions (red) show residues within 4 Å of the opposite subunit. It should be noted that there is only one LB1–LB1 interaction interface for the inactive CaSR, and its total buried surface area is much smaller than that of the active CaSR with four different contact interfaces.

Figure 2—figure supplement 4. Cryo-EM processing workflow of inactive CaSR bound to NB-2D11 in GDN.

(A) The flow chart displaying the cryo-EM processing of inactive CaSR bound to NB-2D11 in GDN. (B) Cryo-EM class averages of inactive CaSR bound to NB-2D11 in GDN micelles. (C) Local resolution map of inactive CaSR bound to NB-2D11. (D) Gold standard Fourier shell correlation (FSC) curve indicates that the overall map for inactive CaSR bound to NB-2D11 reaches nominal resolutions of 6.0 Å at FSC = 0.143. (E) Particle angular distribution of the final cryo-EM reconstruction of inactive CaSR bound to NB-2D11.

Figure 2—figure supplement 5. Comparisons of the structures of CaSR in different conformations.

(A) The superimposition of CaSR^agonist+PAM (purple) and CaSR^Acc (lavender, PDB:7DTV) displays the similar structures with the r.m.s.d of 1.299 Å. (B–D) The superimpositions of CaSR^agonist+PAM (purple) and CaSR^Acc (lavender, PDB:7DTV) in intersubunit (B), the VFT (C), and 7TMD (D) regions. (E) The superimposition of CaSR^{fully inactive} (cyan) and CaSR^Icc (brown, PDB:7DTW) presents a significant difference with the r.m.s.d of 8.007 Å. (F–H) The alignment of CaSR^{fully inactive} (cyan) and CaSR^Icc (brown, PDB:7DTW) in intersubunit (F), the VFT (G), and 7TMD (H) regions. (H) The superimpositions of CaSR^agonist+PAM (purple), CaSR^Acc (lavender, PDB:7DTV), and CaSR^Icc (brown, PDB:7DTW) for VFT domain.