3QHR:
reference: Briefly Bound to Activate: Transient Binding of a Second Catalytic Magnesium Activates the Structure and Dynamics of CDK2 Kinase for Catalysis., Bao ZQ, Jacobsen DM, Young MA, Structure. 2011 May 11;19(5):675-90. PMID: 21565702

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