3EHG:
reference: Structural and enzymatic insights into the ATP binding and autophosphorylation mechanism of a sensor histidine kinase., Trajtenberg F, Grana M, Ruetalo N, Botti H, Buschiazzo A, J Biol Chem. 2010 Aug 6;285(32):24892-903. Epub 2010 May 27. PMID: 20507988

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