Figure 1

Ribbon diagrams of the proteinase K and the homology models of cuticle-degrading proteases: (A) 1IC6, (B) PR1, (C) VCP1 and (D) Ver112. The α helices are colored red, β strands are colored yellow, loops are colored green, substrate-binding segments 100–104 and 132–136 (1IC6 numbering) are colored purple, and disulfide bridges are colored orange. The residues of catalytic triad (Asp39, His69 and Ser224), oxyanion hole (Asn161), disulfide bridges (S-S), and calcium binding sites are represented as stick models. The Ca1 site comprising Pro175, Val/Ala177 and Asp200 is present in all four proteases while the Ca2 site comprising Thr16 and Asp260 is present only in 1IC6.