A protein kinase (PPdPK) was purified from plasma membranes of human placenta. Phosphorylation of casein, but not of phosvitin or lactalbumin, by [γ-32P]ATP in the presence of PPdPK was stimulated about 10-fold by naturally occurring polypeptides prepared from avariety of sources similar to the procedure of Roberts et al. (Proc. Natl. Acad. Sci. U.S.A. 77, 3494–3498, 1980). The amino acid phos-phorylated on casein was serine. According to gel exclusion chromatography the mol. wt, of PPdPK was 95 000. In autoradiograms, following polyacrylamide-gel electrophoresis, the autophosphorylation of PPdPK was greatly enhanced by the polypeptide activators.
A membrane-bound human placental protein kinase activated by endogenous polypeptides
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Mossaad Abdel-Ghany, Shun Nakamura, Javier Navarro, Efraim Racker; A membrane-bound human placental protein kinase activated by endogenous polypeptides. Biosci Rep 1 March 1983; 3 (3): 275–282. doi: https://doi.org/10.1007/BF01122460
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