2Y3F:
reference: How the biotin-streptavidin interaction was made even stronger: investigation via crystallography and a chimeric tetramer., Chivers CE, Koner AL, Lowe ED, Howarth M, Biochem J. 2011 Jan 18. PMID: 21241253

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