3FFA:
reference: Structural Evidence for a Sequential Release Mechanism for Activation of Heterotrimeric G Proteins., Kapoor N, Menon ST, Chauhan R, Sachdev P, Sakmar TP, J Mol Biol. 2009 Aug 22. PMID: 19703466

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