[Protein modulator of cyclic nucleotide-dependent protein kinases from the shrimp Palaemon adspersus]

A thermostable protein modulator of cyclic nucleotide-dependent protein kinases was isolated and purified from the tissue of the shrimp Palaemon adspersus. The molecular weight, N-terminal amino acid and amino acid composition of the protein modulator were determined and its effects on cAMP-dependent protein kinase depending on substrate and cation concentrations were investigated. The protein modulator under study is a low molecular weight (15 000) acid protein, pI-435, which exerts both strong activating and inhibitory effects on cAMP-dependent protein kinase in the reactions of phosphorylation of protamine and histones, respectively.