(32P)Phosphoryl Transfer by Endogenous Protein Kinase at the Ehrlich Cell Surface into Extrinsic Acceptor Proteins

Abstract

The presence of protein kinase(s) at the outer surface of Ehrlich mouse ascites tumour cells has been established. Endogenous protein of the cell surface as well as extrinsic proteins such as phosvitin and histone can act as acceptors for the (γ³²P)-phosphoryl group of ATP. Phosvitin is much more effective as acceptor protein than either the endogeneous protein or the histone protein. The transfer of phosphoryl groups into the phosvitin molecule by the membrane-associated protein kinase is not further stimulated by cyclic AMP. The preferential transfer into phosvitin, rather than into histone, is discussed.