Molecular cloning of cDNAs encoding two isoforms of the catalytic subunit of protein phosphatase 2A

Clones coding for the catalytic subunit of one of the major protein phosphatases (type 2A) were isolated from a porcine cDNA library. Sequence analysis indicated that two different mRNA species coded for this enzyme. The deduced amino acid sequences of the two forms (alpha and beta) of the enzyme were 98% identical and showed 95% identity with the partial sequence of the rabbit enzyme determined by amino acid sequencing. The use of specific oligonucleotide probes indicated that the mRNAs coding for the alpha and beta forms were about 2 kilobases in length, present in equal amounts in a porcine cell line (LLC-PK1), and were the products of two distinct genes. Southern analysis using the coding region of the alpha phosphatase cDNA as a probe suggested the existence of additional related phosphatase genes.