Figure 5.

Ribbon diagram defining secondary structure element of AST. The loops that determine the S1 and subsite specificity of the chymotrypsin fold class of serine proteinases (Perona and Craik 1997) are colored in black: Nβ1-Nβ2 loop (res. 34–41), Nβ3-Nβ4 loop (56–64), the calcium binding loop (74–80), Nβ5-Nβ6 loop (97–103), autolysis loop (143–151), Cα1-Cβ3 loop (169–175), Loop1 (185–188A), and Loop2 (217–225). The most important cold-adapted determinants are shown in black (Met 145, Met 175, Asp 150, Glu 221B), along with the catalytic triad (Asp 102, His 57, Ser 195), Asp 189, the 1BZA inhibitor, the calcium ion, and Gln 192. The autolysis loop (dotted lines) and Tyr 151 of BT are also included.