The leukocyte common antigen (CD45): a putative receptor-linked protein tyrosine phosphatase

Proc Natl Acad Sci U S A. 1988 Oct;85(19):7182-6. doi: 10.1073/pnas.85.19.7182.


A major protein tyrosine phosphatase (PTPase 1B) has been isolated in essentially homogeneous form from the soluble and particulate fractions of human placenta. Unexpectedly, partial amino acid sequences displayed no homology with the primary structures of the protein Ser/Thr phosphatases deduced from cDNA clones. However, the sequence is strikingly similar to the tandem C-terminal homologous domains of the leukocyte common antigen (CD45). A 157-residue segment of PTPase 1B displayed 40% and 33% sequence identity with corresponding regions from cytoplasmic domains I and II of human CD45. Similar degrees of identity have been observed among the catalytic domains of families of regulatory proteins such as protein kinases and cyclic nucleotide phosphodiesterases. On this basis, it is proposed that the CD45 family has protein tyrosine phosphatase activity and may represent a set of cell-surface receptors involved in signal transduction. This suggests that the repertoire of signal transduction mechanisms may include the direct control of an intracellular protein tyrosine phosphatase, offering the possibility of a regulatory balance with those protein tyrosine kinases that act at the internal surface of the membrane.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antigens, Differentiation / analysis
  • Antigens, Differentiation / metabolism*
  • Base Sequence
  • Histocompatibility Antigens / analysis
  • Histocompatibility Antigens / metabolism*
  • Humans
  • Leukocyte Common Antigens
  • Mice
  • Molecular Sequence Data
  • Phosphoprotein Phosphatases / analysis
  • Phosphoprotein Phosphatases / metabolism*
  • Protein Tyrosine Phosphatase, Non-Receptor Type 1
  • Protein Tyrosine Phosphatases
  • Rats
  • Signal Transduction


  • Antigens, Differentiation
  • Histocompatibility Antigens
  • Phosphoprotein Phosphatases
  • Leukocyte Common Antigens
  • Protein Tyrosine Phosphatase, Non-Receptor Type 1
  • Protein Tyrosine Phosphatases

Associated data