Overall structures of CLK/CX-4945 complexes. (a) Overall structure of the CLK1/CX-4945 complex. Both the N-lobe and C-lobe are colored in cyan and blue, respectively. The ligand CX-4945 is shown in yellow with nitrogen, oxygen, and chlorine colored in blue, red, and black, respectively. The common features of CLK (EHLAMMERILG motif, MAPK-like insertion, and Î²-hairpin insertion) are indicated by black boxes, and the amino acid sequences corresponding to these parts are shown below. (b) Overall structure of the CLK2/CX-4945 complex. The N-lobe and C-lobe are colored in blue and light green, respectively. CX-4945 is shown in yellow. (c) Overall structure of the CLK3/CX-4945 complex. The N-lobe and C-lobe are colored in blue and pink, respectively. The structures of CLK1, CLK2, and CLK3 are presented in the same orientation.