3E8L:
reference: The ternary structure of the double-headed arrowhead protease inhibitor API-A complexed with two trypsins reveals a novel reactive site conformation., Bao R, Zhou CZ, Jiang C, Lin SX, Chi CW, Chen Y, J Biol Chem. 2009 Sep 25;284(39):26676-84. Epub 2009 Jul 28. PMID: 19640842

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