Hydrophobic Interaction between the SH2 Domain and the Kinase Domain Is Required for the Activation of Csk |
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Authors: | Esa T Mikkola Carl G Gahmberg |
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Institution: | Division of Biochemistry, Department of Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, FIN-00014 Helsinki, Finland |
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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 β3-αC 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 β3-αC loop. The mutation of the β3-αC 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 β3-αC loop Ala228 to the hydrophobic pocket formed by the side chains of Tyr116, Tyr133, Leu138, and Leu149 on the surface of the SH2 domain. |
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Keywords: | Csk C-terminal Src kinase SH Src homology Cbp Csk binding protein pEY polyamino acid poly(Glu Tyr) HEK-293 human embryonic kidney 293 Chk Csk homologous kinase BSA bovine serum albumin EDTA ethylenediaminetetraacetic acid |
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