THE DESIGN OF PEPTIDE-BASED SUBSTRATES FOR THE CDC2 PROTEIN-KINASE

The substrate sequence specificity of the cdc2 protein kinase from Pis aster ochraceus has been evaluated. The peptide, Ac-Ser-Pro-Gly-Arg-Ar g-Arg-Arg-Lys-amide, serves as an efficient cdc2 kinase substrate with a K-m of 1.50 +/- 0.04 mu M and a V-max. of 12.00 +/- 0.18 mu mol/min per mg. The amino acid sequence of this peptide is not based on any s equence in a known protein substrate of the cyclin-dependent kinase, b ut rather was designed from structural attributes that appear to be im portant in the majority of cdc2 substrates. This cyclin-dependent enzy me is remarkably indiscriminate in its ability to recognize and phosph orylate peptides that contain an assortment of structurally diverse re sidues at the P - 2, P - 1 and P + 2 positions. However, peptides that contain a free N-terminal serine or lack an arginine at the P + 4 pos ition are relatively poor substrates. These aspects of the substrate s pecificity of the cdc2 protein kinase are compared and contrasted with the previously reported substrate specificity of a cdc2-like protein kinase from bovine brain.