Briefly Bound to Activate: Transient Binding of a Second Catalytic Magnesium Activates the Structure and Dynamics of CDK2 Kinase for Catalysis.Bao, Z.Q., Jacobsen, D.M., Young, M.A.
(2011) Structure 19: 675-690
- PubMed: 21565702
- DOI: https://doi.org/10.1016/j.str.2011.02.016
- Primary Citation of Related Structures:
- PubMed Abstract:
We have determined high-resolution crystal structures of a CDK2/Cyclin A transition state complex bound to ADP, substrate peptide, and MgF(3)(-). Compared to previous structures of active CDK2, the catalytic subunit of the kinase adopts a more closed conformation around the active site and now allows observation of a second Mg(2+) ion in the active site. Coupled with a strong [Mg(2+)] effect on in vitro kinase activity, the structures suggest that the transient binding of the second Mg(2+) ion is necessary to achieve maximum rate enhancement of the chemical reaction, and Mg(2+) concentration could represent an important regulator of CDK2 activity in vivo. Molecular dynamics simulations illustrate how the simultaneous binding of substrate peptide, ATP, and two Mg(2+) ions is able to induce a more rigid and closed organization of the active site that functions to orient the phosphates, stabilize the buildup of negative charge, and shield the subsequently activated γ-phosphate from solvent.
Department of Biological Chemistry and the Bioinformatics Program, The University of Michigan Medical School, Ann Arbor, MI 48109, USA.