5WRT:
reference: Structural and Biochemical Characterization of Apicomplexan Inorganic Pyrophosphatases., Jamwal A, Yogavel M, Abdin MZ, Jain SK, Sharma A, Sci Rep. 2017 Jul 12;7(1):5255. doi: 10.1038/s41598-017-05234-y. PMID: 28701714

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