INHIBITION OF CYCLIN-DEPENDENT KINASES BY PURINE ANALOGS - CRYSTAL-STRUCTURE OF HUMAN CDK2 COMPLEXED WITH ROSCOVITINE

Cyclin-dependent kinases (cdk) control the cell division cycle (cdc). These kinases and their regulators are frequently deregulated in human tumours. A potent inhibitor of cdks, roscovitine droxyethylamino)-6-b enzylamino-9-isopropylpurine], was identified by screening a series of C2,N-6,N9-substituted adenines on purified cdc2/cyclin B. Roscovitine displays high efficiency and high selectivity (Meijer, L., Borgne, A. , Mulner, O., Chong, J. P. J., Blow, J. J., Inagaki, N., Inagaki, M., Delcros, J.-G. & Moulinoux, J.-P. (1997) Eur. J. Biochem. 243, 527-536 ). It behaves as a competitive inhibitor for ATP binding to cdc2. We d etermined the crystal structure of a complex between cdk2 and roscovit ine at 0.24-nm (2.4 Angstrom) resolution and refined to an R(factor) o f 0.18. The purine portion of the inhibitor binds to the adenine bindi ng pocket of cdk2. The position of the benzyl ring group of the inhibi tor enables the inhibitor to make contacts with the enzyme not observe d in the ATP-complex structure. Analysis of the position of this benzy l ring explains the specificity of roscovitine in inhibiting cdk2. The structure also reveals that the (R)-stereoisomer of roscovitine is bo und to cdk2. The (R)-isomer is about twice as potent in inhibiting cdc 2/cyclin B than the (S)-isomer. Results from structure/activity studie s and from analysis of the cdk2/roscovitine complex crystal structure should allow the design of even more potent cdk inhibitors.