DIFFERENCES IN SUBSTRATE-SPECIFICITY BETWEEN CDK2-CYCLIN-A AND CDK2-CYCLIN-E IN-VITRO

Cyclin-dependent kinase 2 (Cdk(2)), when bound to either cyclin A or cyclin E, recognizes the Ser/Thr-Pro-X-basic amino acid (motif A) as a phosphorylation site. In this study, we designed several peptides based on motif A and examined the substrate specificity of Cdk2-cyclin A and Cdk2-cyclin E using these peptides, Peptides containing a proline residue in the sequence Pro-X-Thr-Pro-X-basic amino acid (motif B) had higher affinity for both Cdk2 complexes than peptides; containing motif A. Furthermore, differences in substrate affinity between the two Cdk2 complexes were caused by a proline residue adjacent to or three positions before the threonine residue. Similarly, the presence of different basic amino acids in motif B also had different effects on affinity for each complex. We demonstrate the possibility that the substrate specificity of Cdk2 bound to cyclin might be regulated by the species of cyclin. (C) 1995 Academic Press, Inc.