Modification of Ser59 in the unique N-terminal region of tyrosine kinase p56lck regulates specificity of its Src homology 2 domain.
During T-cell activation, Ser59 in the unique N-terminal region of p56lck is phosphorylated. Mutation of Ser59 to Glu59 mimics Ser59 phosphorylation, and upon CD4 crosslinking, this mutant p56lck induces tyrosine phosphorylation of intracellular proteins distinct from those induced by wild-type p56lck. Mutant and wild-type p56lck have similar affinities for CD4 and similar kinase activities. In glutathione S-transferase fusion proteins, the p56lck Src homology 2 (SH2) domain with the SH3 domain and the unique N-terminal region (including Ser59) has a different binding specificity for phosphotyrosyl proteins than the SH2 domain alone. Either deletion of the unique N-terminal region or mutation of Ser59 to Glu59 in the fusion protein reverts the phosphotyrosyl protein binding specificity back to that of the SH2 domain alone. These results suggest that phosphorylation of Ser59 regulates the function of p56lck by controlling binding specificity of its SH2 domain.
Joung
I
I
Division of Tumor Virology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
Kim
T
T
Stolz
L A
LA
Payne
G
G
Winkler
D G
DG
Walsh
C T
CT
Strominger
J L
JL
Shin
J
J
D000595:Amino Acid Sequence; D018698:Glutamic Acid; D005982:Glutathione Transferase / Q000096:biosynthesis; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008213:Lymphocyte Activation; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009856:Oncogene Proteins, Viral / Q000378:metabolism; D010748:Phosphopeptides / Q000737:chemistry / Q000302:isolation & purification; D010766:Phosphorylation; D017354:Point Mutation; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012694:Serine; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology
D009856:Oncogene Proteins, Viral; D010748:Phosphopeptides; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D018698:Glutamic Acid; D012694:Serine; D005982:Glutathione Transferase; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)