Species specificity of antibodies to regulatory subunits of cyclic AMP-dependent protein kinases.

Polyclonal antibodies were generated against regulatory subunits (RI and RII) of type-I and type-II cAMP-dependent protein kinases from rat skeletal muscle. Western immunoblot analyses showed specific cross-reactivity of rat and bovine RI with anti-RI. Similarly, RII from both species was specifically recognized by anti-RII. Quantitative immunoassays, using antisera against proteins from either species, indicated selectivity towards regulatory subunits from the same species. Molecular basis for this selectivity was examined by comparison of peptide maps of 32P-8-azido-cAMP-labelled or autophosphorylated peptides. Detailed analysis of two-dimensional peptide fingerprints demonstrated extensive homology between either RI or RII from the two species. The data suggests that the overall protein-chemical and functional determinants characterizing type-I and type-II regulatory subunits of cyclic AMP dependent protein kinase from different species are substantially similar. However, minor differences in structure, also predicted by amino-acid sequences for RI and RII obtained by molecular cloning, may account for the distinct immunological properties of the proteins from rat and bovine tissues.