Figure 2
Three distinct structural states of the CDK12/CycK complex.
(a) Ribbon representation overview of the complex structures of CDK12715–1038/CycK11–267 and CDK12715–1052/CycK11–267. CDK12 is coloured green, except for the C-terminal kinase extension shown in pink. CycK is coloured light brown. The C-terminal kinase extension, including αK, adopts distinct packing conformations in the different chains in the CDK12715–1052/CycK11–267 structure. AMP-PNP, included in all crystallisations, is observed only in chain A of this structure where its binding is stabilized by the C-terminal extension. All CDK12 subunits were phosphorylated on Thr893 (shown by sticks). (b) Superposition of the CDK12 chains from available crystal structures. In addition to changes in the C-terminal region, there are subtle differences in the packing of the glycine-rich loop, the β4-β5 loop and the tilt of the αC helix. (c) Superposition of the CycK chains from available crystal structures. The apo-structure of CycK (PDB ID: 2I53) shows differences to the complex structures in the region of the H4’ helix in the second cyclin box as well as in the N and C-termini.
