Typical active-site metal coordination geometry for B1, B2, and B3 MBLs (Top). The non-standard Zn(II) coordination spheres for the enzymes SPS-1 (B1) and GOB-18 (B3) are displayed (Bottom). Zn(II) ions and water molecules / hydroxide ions are displayed as grey and red spheres, respectively. For SPS-1, Gly116(bb) and Tyr117(bb) indicate that only the backbone atoms for these residues are represented, while only side chains are represented for all other residues. In images showing binuclear enzymes, Zn1 is displayed at the left, and Zn2 is displayed at the right. The PDB codes for the structures used are: 5N5G (B1 – VIM-1), 3SD9 (B2 – Sfh-I), 3LVZ (B3 – BJP-1), 6CQS (SPS-1), 5K0W (GOB-18).