Figure 1

Structure of casein kinase 1 family members. (A) Homology tree of the casein kinase 1 family consisting of six human casein kinase 1 isoforms: alpha, delta, epsilon, gamma1, gamma2 and gamma3. All available and corresponding protein sequences were retrieved from UniProt (see IDs) and the aligned sequences were used to calculate the average distance tree (using the BLOSUM62 algorithm) visualized with jalview. (B) Schematic drawings of the isoforms show conserved regions (yellow color) especially within the kinase domains (dark blue). Variable regions due to transcript variants and alternative splicing are depicted in light blue resulting in variants differing in protein length: CK1α: 337/365 aa; CK1δ: 409/415 aa; CK1ϵ: 416 aa; CK1γ1 393/422 aa; CK1γ2: 415 aa; CK1γ3: 311–455 aa. Phosphorylation sites (red) are occurring predominantly at the C-terminal ends of the delta (Ser331/370/382/383/384/411) and epsilon isoforms (Ser343/354/362/363/389) and are known to be auto-inhibitory. An additional phosphorylation site can be found within the 28 aa insertion of CK1α (Ser156). A nuclear localization signal is located in the long variant of the alpha isoform (aa 160–163). A centrosomal localization signal [7] is located at the C-terminus in the delta (aa 278–364) isoform.