2ID4:
reference: Differential P1 arginine and lysine recognition in the prototypical proprotein convertase Kex2., Wheatley JL, Holyoak T, Proc Natl Acad Sci U S A. 2007 Apr 17;104(16):6626-31. Epub 2007 Apr 10. PMID: 17426142

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