Identification and differential expression of two forms of regulatory subunits (RII) of cAMP-dependent protein kinase II in Friend erythroleukemic cells. Differentiation and 8-bromo-cAMP elicit a large and selective increase in the rate of biosynthesis of only one type of RII

Monoclonal antibodies as probes of structure, function and isoenzyme forms of the type II regulatory subunit of cyclic AMP-dependent protein kinase

We have attempted to review studies which have utilized monoclonal antibodies in the analysis of various aspects of type II cAMP-dependent protein kinase. It is readily apparent that the monoclonal antibodies directed against RII can be used in a number of ways to assess the structure and function of this protein. Monoclonal antibodies have been used to identify specific structural aspects of the protein, down to the level of amino acid sequence. These have included identification of relationships between several functional domains and the antigenic sites recognized by different antibodies. Monoclonal antibodies also have been used to specifically identify distinct isoenzyme forms of RII. The antibodies were shown to have virtually complete specificity for heart-type RII despite relatively few amino acid substitutions in neural-type RII. This discrimination was utilized to show that purified brain RII is composed of a small fraction of protein similar to the heart isozyme while the bulk of the protein is a distinct isozyme form. It is anticipated that future studies using antibodies specific for individual forms will be a valuable approach to analyzing the distribution and functions of different forms. Monoclonal antibodies have also been used as probes of RII in tissue extracts to examine phosphorylation of this subunit in intact tissue. Monoclonal antibodies should continue to provide powerful probes of the structure and function of this and other protein kinases.