2WBK:
reference: Structure of the Michaelis complex of beta-mannosidase, Man2A, provides insight into the conformational itinerary of mannoside hydrolysis., Offen WA, Zechel DL, Withers SG, Gilbert HJ, Davies GJ, Chem Commun (Camb). 2009 May 14;(18):2484-6. Epub 2009 Apr 6. PMID: 19532864

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