title: Hydrophobic interaction between the SH2 domain and the kinase domain is required for the activation of Csk.
abstract: The protein tyrosine kinase C-terminal Src kinase (Csk) is activated by the engagement of its Src homology (SH) 2 domain. However, the molecular mechanism required for this is not completely understood. The crystal structure of the active Csk indicates that Csk could be activated by contact between the SH2 domain and the beta3-alphaC loop in the N-terminal lobe of the kinase domain. To study the importance of this interaction for the SH2-domain-mediated activation of Csk, we mutated the amino acid residues forming the contacts between the SH2 domain and the beta3-alphaC loop. The mutation of the beta3-alphaC loop Ala228 to glycine and of the SH2 domain Tyr116, Tyr133, Leu138, and Leu149 to alanine resulted in the inability of the SH2 domain ligand to activate Csk. Furthermore, the overexpressed Csk mutants A228G, Y133A/Y116A, L138A, and L149A were unable to efficiently inactivate endogenous Src in human embryonic kidney 293 cells. The results suggest that the SH2-domain-mediated activation of Csk is dependent on the binding of the beta3-alphaC loop Ala228 to the hydrophobic pocket formed by the side chains of Tyr116, Tyr133, Leu138, and Leu149 on the surface of the SH2 domain.
authors.affiliation: Division of Biochemistry, Department of Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, FIN-00014 Helsinki, Finland. Esa.T.Mikkola@Helsinki.fi
authors.forename: Esa T
authors.initials: ET
authors.lastname: Mikkola
authors.forename: Carl G
authors.initials: CG
authors.lastname: Gahmberg
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites / Q000235:genetics; D000081247:CSK Tyrosine-Protein Kinase; D002460:Cell Line; D004789:Enzyme Activation; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry; D018909:src Homology Domains; D019061:src-Family Kinases
chemical_list: D050505:Mutant Proteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D014364:Tryptophan; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human