title: Overexpression, purification, and characterization of SHPTP1, a Src homology 2-containing protein-tyrosine-phosphatase.
abstract: A protein-tyrosine-phosphatase (PTPase; EC 3.1.3.48) containing two Src homology 2 (SH2) domains, SHPTP1, was previously identified in hematopoietic and epithelial cells. By placing the coding sequence of the PTPase behind a bacteriophage T7 promoter, we have overexpressed both the full-length enzyme and a truncated PTPase domain in Escherichia coli. In each case, the soluble enzyme was expressed at levels of 3-4% of total soluble E. coli protein. The recombinant proteins had molecular weights of 63,000 and 45,000 for the full-length protein and the truncated PTPase domain, respectively, as determined by SDS/PAGE. The recombinant enzymes dephosphorylated p-nitrophenyl phosphate, phosphotyrosine, and phosphotyrosyl peptides but not phosphoserine, phosphothreonine, or phosphoseryl peptides. The enzymes showed a strong dependence on pH and ionic strength for their activity, with pH optima of 5.5 and 6.3 for the full-length enzyme and the catalytic domain, respectively, and an optimal NaCl concentration of 250-300 mM. The recombinant PTPases had high Km values for p-nitrophenyl phosphate and exhibited non-Michaelis-Menten kinetics for phosphotyrosyl peptides.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
authors.forename: D
authors.initials: D
authors.lastname: Pei
authors.forename: B G
authors.initials: BG
authors.lastname: Neel
authors.forename: C T
authors.initials: CT
authors.lastname: Walsh
mesh_terms: D000595:Amino Acid Sequence; D017123:Bacteriophage T7 / Q000235:genetics; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D016391:Genes, src / Q000235:genetics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D013379:Substrate Specificity
chemical_list: D011994:Recombinant Proteins; D012965:Sodium Chloride; D017027:Protein Tyrosine Phosphatases