Protein kinase in sea urchin gametes and embryos

A protein kinase which phosphorylates histones and protamine was shown to be present in the sperm, oocyte and developing embryo of the sea urchin, Lytechinus variegatus. The egg and sperm protein kinase activities have a similar pH optimum, pH 7.7 for protamine; and both activities are dependent on cyclic AMP or cyclic GMP. The response to cyclic nucleotides is also similar (maximal at 1 × 10⁻⁴ M for cyclic GMP and 4 × 10⁻⁶ M for cyclic AMP). Levels of protein kinase in the sperm (expressed as units/mg soluble protein) were 30-fold higher than those of the oocytes or gastrula embryos.