3N5K:
reference: Ion pathways in the sarcoplasmic reticulum Ca2+-ATPase., Bublitz M, Musgaard M, Poulsen H, Thogersen L, Olesen C, Schiott B, Morth JP, Moller JV, Nissen P, J Biol Chem. 2013 Feb 11. PMID: 23400778

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