title: The SH3 domain of Bruton's tyrosine kinase displays altered ligand binding properties when auto-phosphorylated in vitro.
abstract: Btk is a member of the Tec family of protein tyrosine kinases expressed in B cells. It is stimulated following cross-linking of the B cell receptor which leads to the autophosphorylation of a specific residue in the SH3 domain, Y223. Previous work using Btk-derived fusion proteins has shown that the Btk SH3 domain binds to c-Cbl and Wiskott-Aldrich syndrome protein (WASP) in vitro. We show here that when the Btk SH3 domain fusion protein is autophosphorylated, its ability to take part in protein interactions is altered as compared to the non-phosphorylated fusion protein. Although the phosphorylated Btk SH3 domain still binds c-Cbl, it no longer binds WASP and instead acquires a high affinity for kinase-active Syk. The region of Syk responsible for this interaction is contained within its C terminus, suggesting a novel mechanism by which these proteins may interact.
authors.affiliation: Institute of Child Health, University College London, GB.
authors.forename: L M
authors.initials: LM
authors.lastname: Morrogh
authors.forename: S
authors.initials: S
authors.lastname: Hinshelwood
authors.forename: P
authors.initials: P
authors.lastname: Costello
authors.forename: G O
authors.initials: GO
authors.lastname: Cory
authors.forename: C
authors.initials: C
authors.lastname: Kinnon
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology / Q000276:immunology; D016367:Baculoviridae / Q000235:genetics; D001665:Binding Sites; D001667:Binding, Competitive; D002460:Cell Line; D004792:Enzyme Precursors / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D050721:Proto-Oncogene Proteins c-cbl; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D018411:Spodoptera; D000072377:Syk Kinase; D044767:Ubiquitin-Protein Ligases; D014923:Wiskott-Aldrich Syndrome / Q000378:metabolism; D051316:Wiskott-Aldrich Syndrome Protein; D018909:src Homology Domains
chemical_list: D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; C495767:WAS protein, human; D051316:Wiskott-Aldrich Syndrome Protein; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; C000606896:SYK protein, human; D000072377:Syk Kinase; C067419:CBL protein, human