3I77:
reference: Combinatorial enzyme design probes allostery and cooperativity in the trypsin fold., Page MJ, Di Cera E, J Mol Biol. 2010 Jun 4;399(2):306-19. Epub 2010 Apr 24. PMID: 20399789

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