ANTI-HEAD AND ANTI-TAIL ANTIBODIES AGAINST DISTINCT EPITOPES IN THE CATALYTIC SUBUNIT OF PROTEIN-KINASE-A - USE IN THE STUDY OF THE KINASE SPLITTING MEMBRANAL PROTEINASE KSMP

Protein kinases share a considerable sequence homology in their cataly tic core (residues 40-300 in PKA). Each core is flanked by ''head'' an d ''tail'' segments at its amino- and carboxy-termini, which are diffe rent in the various kinases. These end segments may play an important role in creating the preferential affinity of each kinase for its phys iological substrates or regulatory ligands. Here we describe three ant ipeptide antibodies (alpha P-1, alpha P-2, and alpha P-3) that specifi cally recognize the head and tail segments of the catalytic subunit (C ) of PKA. (i) alpha P-1 (against (6)A-K-23) react with C when denature d but not when in its native structure; (ii) alpha P-2 (against K-319- I-335), bind to the site in C cleaved by the kinase splitting membrana l proteinase (KSMP) and inhibit this cleavage of C; (iii) alpha P-3 (a gainst S-338-F-350) react with C but not with the KSMP cleavage produc t C', useful for detecting a KSMP-like activity in different tissues a nd subcellular loci. The combined use of the antibodies described here provides a strict definition of C, and thus a high degree of fidelity in its biorecognition.