2H6I:
reference: Conversion of protein farnesyltransferase to a geranylgeranyltransferase., Terry KL, Casey PJ, Beese LS, Biochemistry. 2006 Aug 15;45(32):9746-55. PMID: 16893176

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