A rat cDNA encoding a non-receptor type phosphotyrosine phosphatase (PTPase; EC 3.1.3.48) was identified. The 1608 bp cDNA contains a single open reading frame that predicts a 382 amino acid protein with M r 44,438. The predicted protein has no apparent signal or transmembrane sequences, suggesting that it is a cytosolic protein. The C-terminal region has a PTPase catalytic domain that has 40–50% nucleic acid homology to other known PTPases. The N-terminal region has little amino acid sequence homology to any other known sequences. The recombinant protein of the cloned cDNA expressed in Escherichia coli was shown to possess PTPase activity using myelin basic protein, tyrosine phosphorylated by p43ν-abl tyrosine kinase, as a substrate.
