2XTZ:
reference: The crystal structure of a self-activating G protein {alpha} subunit reveals its distinct mechanism of signal initiation., Jones JC, Duffy JW, Machius M, Temple BR, Dohlman HG, Jones AM, Sci Signal. 2011 Feb 8;4(159):ra8. PMID: 21304159

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