Fig. 39.

Coordination site for Zn²⁺ binding in GluN2A and GluN2B NTDs. (A) Crystal structure of GluN1 (slate)/GluN2B (gray) heterodimeric NTDs (PDB: 5TPW). Zn²⁺ binds within the cleft of the bilobed clamshell-like NTD. (B) Four residues within the bilobed GluN2A NTD coordinate Zn²⁺, resulting in high-affinity binding. (C) Crystal structure of Zn²⁺-bound GluN2B NTD (PDB: 3JPY). Zn²⁺ is coordinated by only two residue side chains, which accounts for its lower affinity compared with GluN2A.