title: Protein tyrosine phosphatase domains from the protochordate Styela plicata.
abstract: Protein tyrosine phosphorylation is an important regulatory mechanism in cell physiology. While the protein tyrosine kinase (PTKase) family has been extensively studied, only six protein tyrosine phosphatases (PTPases) have been described. By Southern blot analysis, genomic DNA from several different phyla were found to cross-hybridize with a cDNA probe encoding the human leukocyte-common antigen (LCA; CD45) PTPase domains. To pursue this observation further, total mRNA from the protochordate Styela plicata was used as a template to copy and amplify, using polymerase chain reaction (PCR) technology, PTPase domains. Twenty-seven distinct sequences were identified that contain hallmark residues of PTPases; two of these are similar to described mammalian PTPases. Southern blot analysis indicates that at least one other Styela sequence is highly conserved in a variety of phyla. Seven of the Styela domains have significant similarity to each other, indicating a subfamily of PTPases. However, most of the sequences are disparate. A comparison of the 27 Styela sequences with the ten known PTPase domain sequences reveals that only three residues are absolutely conserved and identifies regions that are highly divergent. The data indicate that the PTPase family will be equally as large and diverse as the PTKases. The extent and diversity of the PTPase family suggests that these enzymes are, in their own right, important regulators of cell behavior.
authors.affiliation: Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110.
authors.forename: R J
authors.initials: RJ
authors.lastname: Matthews
authors.forename: E
authors.initials: E
authors.lastname: Flores
authors.forename: M L
authors.initials: ML
authors.lastname: Thomas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000943:Antigens, Differentiation / Q000235:genetics; D001483:Base Sequence; D005075:Biological Evolution; D002107:Caenorhabditis / Q000235:genetics; D002816:Chordata, Nonvertebrate / Q000201:enzymology* / Q000235:genetics*; D006649:Histocompatibility Antigens / Q000235:genetics; D006801:Humans; D017493:Leukocyte Common Antigens; D008969:Molecular Sequence Data; D005810:Multigene Family; D010749:Phosphoprotein Phosphatases / Q000235:genetics*; D019000:Phosphotyrosine; D017027:Protein Tyrosine Phosphatases; D012689:Sequence Homology, Nucleic Acid; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D000943:Antigens, Differentiation; D006649:Histocompatibility Antigens; D019000:Phosphotyrosine; D014443:Tyrosine; D010749:Phosphoprotein Phosphatases; D017493:Leukocyte Common Antigens; D017027:Protein Tyrosine Phosphatases