MOLECULAR-CLONING OF A 74-KDA REGULATORY SUBUNIT (B'' OR DELTA) OF HUMAN PROTEIN PHOSPHATASE-2A

Based on amino acid sequence data of a 74-kDa regulatory subunit (B '' or delta) of a human heterotrimeric protein phosphatase 2A, a cDNA en coding the subunit was isolated from a human cerebral cortex library. The cDNA had an open reading frame encoding an M(r) 66 138 protein of 570 amino acids. Bacterial expression of the cDNA yielded a protein im munoreactive with antisera specific to the 74-kDa subunit, The predict ed primary structure of the subunit had no similarity to already repor ted sequences of PP2A regulatory subunits including A, B, and PR72. Po tential phosphorylation sites for protein kinases A and C, a bipartite motif of putative nuclear localization signal, an SH3 accessible prol ine-rich domain, and a unique PQ repeat were found in the sequence. Th e subunit mRNA of about 2.9 kb was ubiquitously expressed in rat tissu es.