5rsa is a 1 chain structure with sequence from Bos taurus. This structure supersedes the now removed PDB entries and 2rsa. The September 2008 RCSB PDB Molecule of the Month feature on Ribonuclease A by David Goodsell is 10.2210/rcsb_pdb/mom_2008_9. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.