Figure 4

SCs illustrate catalytic triad diversity among serine proteases. Comparing the geometry of the ubiquitous HIS-ASP-SER catalytic triad across 730 structures, 52 species, and 7 EC families demonstrates the scalability of FASST to large numbers of structures and the ability of FASST to detect substructure variation among non-divergently related families. All of the divergently-related families of the chymotrypsin clan cluster into a dense sub-group while the convergently-related subtilisin family forms a separate cluster within the SCs. The highly diverse family of lipases form several smaller clusters distinct from both the chymotrypsin-like and subtilisin-like structures. Several trypsin outlier structures are labeled and the references corresponding to each PDB entry document sources of catalytic site deviation. Light gray ellipses denote automatically identified clusters. The open/closed plot characters correspond to apo/holo structures, respectively.