4ARF:
reference: Structural basis for activity regulation and substrate preference of clostridial collagenases G, H, and T., Eckhard U, Schonauer E, Brandstetter H, J Biol Chem. 2013 May 23. PMID: 23703618

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