The substrate sequence specificity of the cdc2 protein kinase from Pisaster ochraceus has been evaluated. The peptide, Ac-Ser-Pro-Gly-Arg-Arg-Arg-Arg-Lys-amide, serves as an efficient cdc2 kinase substrate with a Km of 1.50 +/- 0.04 microM and a Vmax. of 12.00 +/- 0.18 mumol/min per mg. The amino acid sequence of this peptide is not based on any sequence in a known protein substrate of the cyclin-dependent kinase, but rather was designed from structural attributes that appear to be important in the majority of cdc2 substrates. The cyclin-dependent enzyme is remarkably indiscriminate in its ability to recognize and phosphorylate peptides that contain an assortment of structurally diverse residues 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 position are relatively poor substrates. These aspects of the substrate specificity of the cdc2 protein kinase are compared and contrasted with the previously reported substrate specificity of a cdc2-like protein kinase from bovine brain [Beaudette, Lew and Wang (1993) J. Biol. Chem. 268, 20825-20830].

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