Fig. 2.

Zn²⁺-binding sites. (Left and Center) Stereoview of two Zn²⁺-binding sites with protein ligands along with a 2Fo – Fc map contoured at 6 σ. Each A2 subunit provides one complete Zn²⁺-binding site involving three His ligands and shares two others at interfaces with neighboring A2 subunits. The refined Zn²⁺ positions are shown as purple balls. (Right) The arrangement of Zn²⁺-binding sites near the molecular threefold axis of R. pachyptila C1 Hb. Zn²⁺ ions are purple, along with protein ligands and main-chain traces in the vicinity of the Zn²⁺ ions.