4PGA:
reference: Ion binding induces closed conformation in Pseudomonas 7A glutaminase-asparaginase (PGA): crystal structure of the PGA-SO4(2-)-NH4+ complex at 1.7 A resolution., Jakob CG, Lewinski K, LaCount MW, Roberts J, Lebioda L, Biochemistry 1997 Jan 28;36(4):923-31. PMID: 9020792

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