Protein kinases in developing rat brain.

The levels of cAMP-dependent protein kinases were measured in developing rat brain by a variety of methods. The regulatory subunit (R) was measured both by [3H]cAMP binding and by 8-N3-[32P]cAMP incorporation. The catalytic subunit (C) was measured by an assay of histone kinase activity. Data were calculated per mg protein. Neither R nor C levels changed significantly in either membranes or cytosol during development. The ratio of R to C was essentially unity in the cerebra of both newborn (2-day-old) and adult (40-day-old) rats. Polyacrylamide-gel electrophoresis resolved two regulatory subunits (R-I) and (R-II) which were derived from the Type I and Type II cAMP-dependent protein kinases, respectively. 8-N3-[32P]cAMP incorporation into Proteins R-I and R-II indicated that the amounts of Proteins R-I and R-II did not change significantly in either membranes or cytosol during development.