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 c yclin E, recognizes the Ser/Thr-Pro-X-basic amino acid (motif A) as a phosphorylation site. In this study, we designed several peptides base d on motif A and examined the substrate specificity of Cdk2-cyclin A a nd Cdk2-cyclin E using these peptides, Peptides containing a proline r esidue in the sequence Pro-X-Thr-Pro-X-basic amino acid (motif B) had higher affinity for both Cdk2 complexes than peptides; containing moti f A. Furthermore, differences in substrate affinity between the two Cd k2 complexes were caused by a proline residue adjacent to or three pos itions before the threonine residue. Similarly, the presence of differ ent basic amino acids in motif B also had different effects on affinit y 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.