3KYI:
reference: Using structural information to change the phosphotransfer specificity of a two-component chemotaxis signalling complex., Bell CH, Porter SL, Strawson A, Stuart DI, Armitage JP, PLoS Biol. 2010 Feb 9;8(2):e1000306. PMID: 20161720

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