1IB4:
reference: The X-ray structure of Aspergillus aculeatus polygalacturonase and a modeled structure of the polygalacturonase-octagalacturonate complex., Cho SW, Lee S, Shin W, J Mol Biol 2001 Aug 24;311(4):863-78. PMID: 11518536

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