A 1.5 kb clone containing the full-length coding sequence of a type-1 protein phosphatase catalytic subunit has been isolated from a rabbit skeletal muscle cDNA library constructed in λgt10. The protein sequence deduced from the cDNA contains 311 residues and has a molecular mass of 35.4 kDa. A single mRNA species at 1.6 kb was visualized by Northern blotting. The type-1 protein phosphatase was strikingly homologous to protein phosphatase 2A, 49% of the amino acids between residues 11 and 280 being identical. The first 10 and last 31 residues were dissimilar. Residues 1–101 of the type-1 protein phosphatase also showed 21% sequence identity with a region of mammalian alkaline phosphatases.
