Basic region of residues 228-231 of protein kinase CK1alpha is involved in its interaction with axin: binding to axin does not affect the kinase activity.
Protein kinase CK1, also known as casein kinase 1, participates in the phosphorylation of beta-catenin, which regulates the functioning of the Wnt signaling cascade involved in embryogenesis and carcinogenesis. beta-catenin phosphorylation occurs in a multiprotein complex assembled on the scaffold protein axin. The interaction of CK1alpha from Danio rerio with mouse-axin has been studied using a pull-down assay that uses fragments of axin fused to glutathione S transferase, which is bound to glutathione sepharose beads. The results indicate that the three lysines present in the basic region of residues 228-231 of CK1alpha are necessary for the binding of CK1 to axin. Lysine 231 is particularly important in this interaction. In order to define the relevance of the axin-CK1alpha interaction, the effect of the presence of axin on the phosphorylating activity of CK1alpha was tested. It is also evident that the region of axin downstream of residues 503-562 is required for CK1alpha interaction. The binding of CK1alpha to axin fragment 292-681 does not facilitate the phosphorylation of beta-catenin despite the fact that this axin fragment can also bind beta-catenin. Binding of CK1alpha to axin is not required for the phosphorylation of axin itself and, likewise, axin does not affect the kinetic parameters of the CK1alpha towards casein or a specific peptide substrate.[1]References
- Basic region of residues 228-231 of protein kinase CK1alpha is involved in its interaction with axin: binding to axin does not affect the kinase activity. Sobrado, P., Jedlicki, A., Bustos, V.H., Allende, C.C., Allende, J.E. J. Cell. Biochem. (2005) [Pubmed]
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