Figure 2.

Molecular determination of substrate specificity in the granzyme B crystal structure. (a) Two granzyme B molecules (green) are complexed with a dimer of the inhibitor ecotin (dark and light blue). The key residues at the catalytic site of granzyme B are labeled using orange atoms. (b) The catalytic site of granzyme B is shown as a 2.2Å electron density map, with the primary determinant of substrate specificity, Arg226 (green), held by three hydrogen bonds (from Gln217 and Ser221); the substrate aspartic acid is shown in blue. Reproduced with permission from [5].