3OQN:
reference: Structures of carbon catabolite protein A-(HPr-Ser46-P) bound to diverse catabolite response element sites reveal the basis for high-affinity binding to degenerate DNA operators., Schumacher MA, Sprehe M, Bartholomae M, Hillen W, Brennan RG, Nucleic Acids Res. 2010 Nov 23. PMID: 21106498

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