3DGE:
reference: Structural insight into partner specificity and phosphoryl transfer in two-component signal transduction., Casino P, Rubio V, Marina A, Cell. 2009 Oct 16;139(2):325-36. Epub 2009 Oct 1. PMID: 19800110

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