Fig 1. Transition metal binding occurs at a common site in diverse S100 proteins.

Overlay of the crystal structures of S100B (orange, PDB 3CZT) and S100A12 (blue, PDB 1ODB) bound to Ca²⁺ and transition metals. Ions are shown as colored spheres: Ca²⁺ (blue), Zn²⁺ (gray) and Cu²⁺ (copper). Residues ligating the transition metals are are shown as sticks. Boxed region is shown in detail in panel B.