1JUG:
reference: Structure of the calcium-binding echidna milk lysozyme at 1.9 A resolution., Guss JM, Messer M, Costello M, Hardy K, Kumar V, Acta Crystallogr D Biol Crystallogr. 1997 Jul 1;53(Pt 4):355-63. PMID: 15299900

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).