Identification, cloning, and expression of a cytosolic megakaryocyte protein-tyrosine-phosphatase with sequence homology to cytoskeletal protein 4.1.
We have isolated a cDNA encoding a third type of protein-tyrosine-phosphatase. We screened human megakaryoblastic cell line (MEG-01) an umbilical vein endothelial cell cDNA libraries to obtain a 3.7-kilobase cDNA designated PTPase MEG. Northern blot analysis of MEG-01 RNA detected a 3.7-kilobase transcript, suggesting that a full-length cDNA has been identified. PTPase MEG cDNA contains an open reading frame of 926 amino acids. The cDNA has a G+C-rich 5' untranslated region of 771 nucleotides that has the potential to form stable stem-loop structures and has two upstream ATG codons. The predicted protein (Mr = 105,910) has no apparent membrane-spanning region and contains a single protein-tyrosine-phosphatase domain (amino acids 659-909) that is 35-40% identical to previously described tyrosine-phosphatase domains. The recombinant phosphatase domain possesses protein-tyrosine-phosphatase activity when expressed in Escherichia coli. The amino-terminal region (amino acids 31-367) is 45% identical to the amino terminus of human erythrocyte protein 4.1, a cytoskeletal protein. The identification of a protein-tyrosine-phosphatase that is related to cytoskeletal proteins implies that cell signaling activities reside not only in transmembrane receptors but in cytoskeletal elements as well.
Gu
M X
MX
Washington University School of Medicine, Division of Hematology-Oncology, St. Louis, MO 63110.
York
J D
JD
Warshawsky
I
I
Majerus
P W
PW
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D003598:Cytoskeletal Proteins / Q000737:chemistry; D003600:Cytosol / Q000201:enzymology; D004247:DNA / Q000235:genetics; D004926:Escherichia coli; D015870:Gene Expression; D006801:Humans; D008533:Megakaryocytes / Q000201:enzymology*; D008565:Membrane Proteins / Q000737:chemistry; D008969:Molecular Sequence Data; D009479:Neuropeptides; D009841:Oligonucleotides / Q000737:chemistry; D010749:Phosphoprotein Phosphatases / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D054590:Protein Tyrosine Phosphatase, Non-Receptor Type 4; D017027:Protein Tyrosine Phosphatases / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping
D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009479:Neuropeptides; D009841:Oligonucleotides; D012333:RNA, Messenger; D011994:Recombinant Proteins; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1; D004247:DNA; D010749:Phosphoprotein Phosphatases; C516658:PTPN4 protein, human; D054590:Protein Tyrosine Phosphatase, Non-Receptor Type 4; D017027:Protein Tyrosine Phosphatases