Fig. 2.

The homology model of (a) M^proST and (b) M^proSH visualized by Insight II. α-Helices and β-strands are shown in red cylinders and yellow arrows, respectively. The general acid–base catalyst His residue and the nucleophilic Cys residue are labeled. The locations of the putative substrate binding subsites S1 and S2 are indicated.