1NQD:
reference: A bacterial collagen-binding domain with novel calcium-binding motif controls domain orientation., Wilson JJ, Matsushita O, Okabe A, Sakon J, EMBO J 2003 Apr 15;22(8):1743-52. PMID: 12682007

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