3GN9:
reference: Calcium is essential for the major pseudopilin in the type 2 secretion system., Korotkov KV, Gray MD, Kreger A, Turley S, Sandkvist M, Hol WG, J Biol Chem. 2009 Sep 18;284(38):25466-70. Epub 2009 Jul 29. PMID: 19640838

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