Figure 3. Amino acid sequence alignment of SP domains of chymotrypsin, trypsin, C1r, C1r-LP and factor B.

Numbering at the top is for chymotrypsinogen. Arrows indicate the catalytic triad residues, stars indicate residue 189 at the bottom of the S1 pocket and residue 226, which is aspartic residue in C1r-LP and factor B. The conserved newly formed N-terminal sequence of active SPs is indicated by shading. CHM, bovine chymotrypsin; TRP, bovine trypsin; fB, complement factor B.