TI - 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 . AB - 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 .