1N4A:
reference: Crystal structures of the BtuF periplasmic-binding protein for vitamin B12 suggest a functionally important reduction in protein mobility upon ligand binding., Karpowich NK, Huang HH, Smith PC, Hunt JF, J Biol Chem 2003 Mar 7;278(10):8429-34. PMID: 12468528

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