3S7H:
reference: Crystallographic and Kinetic Evidence of Allostery in a Trypsin-like Protease., Niu W, Chen Z, Gandhi PS, Vogt AD, Pozzi N, Pelc LA, Zapata F, Di Cera E, Biochemistry. 2011 Jun 30. PMID: 21707111

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