title: Identification of the site in the Syk protein tyrosine kinase that binds the SH2 domain of Lck.
abstract: The Syk protein tyrosine kinase (PTK) is expressed in many hematopoietic cells and is involved in signaling from various receptors for antigen and Fc portions of IgG and IgE. Upon cross-linking of these receptors, Syk is rapidly phosphorylated on tyrosine residues and enzymatically activated. We and others have found that the Lck kinase, a member of the Src family of PTKs, binds through its Src homology (SH) 2 domain to tyrosine phosphorylated Syk and to the related Zap kinase. Here we report that this interaction is direct and identify the two tandem tyrosines at the autophosphorylation site of Syk, Tyr518, and Tyr519, as the binding site for the SH2 domain of Lck. Mutation of either or both tyrosines to phenylalanines abrogated binding, while mutation of a second repetition of the motif at Tyr539 and Tyr540, or of the three tyrosines in the C terminus of Syk, did not. The SH2 domain of Lck bound the autophosphorylation site only when both Tyr518 and Tyr519 were phosphorylated. In intact cells the binding of the SH2 domain of Lck correlated with the ability of Syk to induce tyrosine phosphorylation of cellular proteins.
authors.affiliation: Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.
authors.forename: C
authors.initials: C
authors.lastname: Couture
authors.forename: M
authors.initials: M
authors.lastname: Deckert
authors.forename: S
authors.initials: S
authors.lastname: Williams
authors.forename: F O
authors.initials: FO
authors.lastname: Russo
authors.forename: A
authors.initials: A
authors.lastname: Altman
authors.forename: T
authors.initials: T
authors.lastname: Mustelin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D004792:Enzyme Precursors / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship; D013552:Swine; D000072377:Syk Kinase; D018909:src Homology Domains
chemical_list: D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D000072377:Syk Kinase