6HDV:
reference: Crystal structure of afifavidin reveals common features of molecular assemblage in the bacterial dimeric avidins., Avraham O, Bayer EA, Livnah O, FEBS J. 2018 Oct 28. doi: 10.1111/febs.14685. PMID: 30369031

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