4DFY:
reference: Structural basis for the regulation of protein kinase A by activation loop phosphorylation., Steichen JM, Kuchinskas M, Keshwani MM, Yang J, Adams JA, Taylor SS, J Biol Chem. 2012 Feb 10. PMID: 22334660

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