3K9M:
reference: Stefin A displaces the occluding loop of cathepsin B only by as much as required to bind to the active site cleft., Renko M, Pozgan U, Majera D, Turk D, FEBS J. 2010 Oct;277(20):4338-45. doi: 10.1111/j.1742-4658.2010.07824.x., Epub 2010 Sep 22. PMID: 20860624

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