1KCD:
reference: Active-site architecture of endopolygalacturonase I from Stereum purpureum revealed by crystal structures in native and ligand-bound forms at atomic resolution., Shimizu T, Nakatsu T, Miyairi K, Okuno T, Kato H, Biochemistry. 2002 May 28;41(21):6651-9. PMID: 12022868

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