2ptn is a 1 chain structure with sequence from Bos taurus. This structure supersedes the now removed PDB entry 1ptn. The October 2003 RCSB PDB Molecule of the Month feature on Trypsin by David S. Goodsell is 10.2210/rcsb_pdb/mom_2003_10. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.