title: The SH3 domain of p56lck is involved in binding to phosphatidylinositol 3'-kinase from T lymphocytes.
abstract: Many of the Src-like tyrosine kinases are thought to participate in multiprotein complexes that modulate transmembrane signalling through tyrosine phosphorylation. We have used in vitro binding studies employing bacterially expressed glutathione S-transferase-p56lck fusion proteins and cell extracts to map regions on p56lck that are involved in binding to phosphatidylinositol 3'-kinase (PI3K). Deletions within the SH3 domain of p56lck abolished binding of PI3K activity from T-cell lysates, whereas deletion of the SH2 domain caused only a slight reduction in the level of PI3K activity bound to p56lck sequences. The binding of PI3K from T-cell extracts to p56lck was not blocked by antiphosphotyrosine antibodies, but p56lck-bound PI3K activity was sensitive to phosphatase treatment. The SH3 domain of p56lck also bound the majority of PI3K activity from uninfected chicken embryo fibroblasts. However, a drastically different binding specificity was observed with use of extracts of Rous sarcoma virus v-src-transformed cells, in which the majority of PI3K activity bound to the SH2 domain of p56lck in a phosphotyrosine-dependent manner. These results suggest that are two modes of PI3K binding to p56lck, and presumably to other Src-like tyrosine kinases. In one mode, PI3K from T cells or uninfected chicken embryo fibroblasts binds predominantly to the SH3 domain of p56lck. In the other mode, involving PI3K from Rous sarcoma virus-transformed cells, binding is largely phosphotyrosine dependent and requires the SH2 domain of p56lck.
authors.affiliation: Department of Medical Biochemistry, University of Calgary Medical Centre, Alberta, Canada.
authors.forename: L B
authors.initials: LB
authors.lastname: Vogel
authors.forename: D J
authors.initials: DJ
authors.lastname: Fujita
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001358:Avian Sarcoma Viruses; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D002472:Cell Transformation, Viral; D002642:Chick Embryo; D006801:Humans; D066298:In Vitro Techniques; D007962:Leukocytes / Q000378:metabolism; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D019000:Phosphotyrosine; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D011993:Recombinant Fusion Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)