Photoaffinity labeling of three renal cyclic 3',5'-adenosine monophosphate-binding proteins

Evidence is presented for the presence of multiple cyclic AMP binding components in the plasma membrane and cytosol fractions of porcine renal cortex and medulla. N6-(Ethyl-2-diazomalonyl)-3',5'-adenosine monophosphate, a photoaffinity label for cyclic AMP binding sites, exhibits non-covalent binding characteristics similar to cyclic AMP in membrane and soluble fractions. Binding data for either compound to the plasma membrane fraction yields biphasic Scatchard plots while triphasic plots are obtained with the dialyzed cytosol. When covalently labeled fractions are separated on SDS-polyacrylamide gel electrophoresis, the cyclic AMP photoaffinity label is found on 49 000 and 130 000 dalton components in each kidney fraction. DEAE-cellulose and gel filtration chromatography of the labeled cortical cytosol fraction establishes that the three components suggested by the binding data correspond to two 49 000 dalton species and a 130 000 component. The 49 000 species have higher affinities for cyclic AMP than the 130 000 component (Ka(1) = 2.0 . 10(9), Ka(2) = 1.7 . 10(8), Ka(3) = 1.0 . 10(7)). The 49 000 components are associated with protein kinase activity while the 130 000 component does not exhibit protein kinase, adenosine deaminase, or cyclic nucleotide phosphodiesterase activity. Immunologic results and effects of phosphorylation and cyclic GMP on cyclic AMP binding further suggest that the 49 000 components are regulatory subunits of cyclic AMP-dependent protein kinases. Cyclic AMP binding to the 130 000 component is markedly inhibited by adenosine and adenine nucleotides, but not cyclic GMP. Thus, this component may reflect an aspect of adenosine control or metabolism which may or may not be a cyclic AMP-related cellular function.