5FNX:
reference: Structures of a bi-functional Kunitz-type STI family inhibitor of serine and aspartic proteases: Could the aspartic protease inhibition have evolved from a canonical serine protease-binding loop?, Guerra Y, Valiente PA, Pons T, Berry C, Rudino-Pinera E, J Struct Biol. 2016 Aug;195(2):259-71. doi: 10.1016/j.jsb.2016.06.014. Epub 2016 , Jun 18. PMID: 27329566

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