5K6P:
reference: A Highly Conserved Yet Flexible Linker Is Part of a Polymorphic Protein-Binding Domain in Myosin-Binding Protein C., Michie KA, Kwan AH, Tung CS, Guss JM, Trewhella J, Structure. 2016 Nov 1;24(11):2000-2007. doi: 10.1016/j.str.2016.08.018. Epub 2016, Oct 6. PMID: 27720588

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