1PEK:
reference: Structure of the complex of proteinase K with a substrate analogue hexapeptide inhibitor at 2.2-A resolution., Betzel C, Singh TP, Visanji M, Peters K, Fittkau S, Saenger W, Wilson KS, J Biol Chem 1993 Jul 25;268(21):15854-8. PMID: 8340410

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