[Phosphorylation of proteins in the kidney papillary zone by endogenous cAMP-dependent protein kinases]

Using SDS-PAAG electrophoresis with subsequent autoradiography, several proteins from plasma membranes and cell cytosol of rat kidney papillary zone were identified as substrates for endogenous cAMP-dependent protein kinases. The cAMP-dependent phosphorylation of plasma membrane proteins was made possible only after the destruction of membrane vesicles. Plasma membrane and cytosol fractions were found to contain a 58 kDa protein whose properties are similar to those of the regulatory subunit of cAMP-dependent protein kinase of the second type. It was shown also that the content of endogenous substrates of cAMP-dependent protein kinases in cell cytosol is higher than that in plasma membranes.