2I07:
reference: Structure of C3b reveals conformational changes that underlie complement activity., Janssen BJ, Christodoulidou A, McCarthy A, Lambris JD, Gros P, Nature. 2006 Nov 9;444(7116):213-6. Epub 2006 Oct 15. PMID: 17051160

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