2XZ3:
reference: Charge-surrounded pockets and electrostatic interactions with small ions modulate the activity of retroviral fusion proteins., Lamb D, Schuttelkopf AW, van Aalten DM, Brighty DW, PLoS Pathog. 2011 Feb 3;7(2):e1001268. PMID: 21304939

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