THE CLEAVAGE OF PROTEIN-KINASE-A BY THE KINASE-SPLITTING MEMBRANAL PROTEINASE IS REPRODUCED BY MEPRIN-BETA

The Kinase-Splitting Membranal Proteinase (KSMP) is a metallo-endoprot einase that clips off the carboxyl terminus tail of the catalytic (C) subunit of protein kinase A to yield a truncated, catalytically inacti ve protein (C'), Here we report (a) a new procedure for the purificati on of KSMP, yielding a major protein band in SDS-polyacrylamide gel el ectrophoresis that correlates with the characteristic KSMP activity; ( b) the sequence of tryptic peptides obtained from this band, suggestin g an identity between this protein and meprin beta; (c) the immune-det ection by specific anti-peptide antibodies of both the alpha and the b eta subunits of meprin in KSMP preparations; (d) the stable expression of meprin beta in a mammalian cell line (293) to establish a clone th at constitutively expresses the full-length precursor of meprin beta; and (e) the optimalization of the proteolytic activation of this precu rsor to obtain an enzyme exhibiting the specific KSMP cleavage, sugges ting that KSMP is either derived from, or identical with, the meprin b eta gene product, It is hoped that these results will shed light on th e possible physiological role of KSMP and the way it may affect protei n kinase A-mediated processes.