Location of the active site in chymotrypsin. Chymotrypsin consists of three chains, shown in ribbon form in orange, blue, and green. The side chains of the catalytic triad residues are shown as ball-and-stick representations. Notice these side chains, including serine 195, lining the active site in the upper half of the structure. Also notice two intrastrand and two interstrand disulfide bonds in various locations throughout the molecule.
[Drawn from 1GCT.pdb.]