2OBG:
reference: High-affinity single-domain binding proteins with a binary-code interface., Koide A, Gilbreth RN, Esaki K, Tereshko V, Koide S, Proc Natl Acad Sci U S A. 2007 Apr 17;104(16):6632-7. Epub 2007 Apr 9. PMID: 17420456

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