Figure 1

Soluble expression of CDK12 requires CycK.

(a) Schematic showing the domain organisation of human CDK12 and CycK (RS, arginine-serine-rich; PRM, proline-rich motifs). (b) Small scale nickel-affinity purifications from 3 mL baculoviral expression of hexahistidine-tagged proteins. Results are shown for a subset of experiments using the indicated CDK12 constructs as well as CycK^11–267 and CycL1^43–320. (c) Deconvoluted intact mass spectra for CDK12^715–1052 purified following co-expression with CycK^11–267. The two mass peaks represent the native protein as well as a larger species containing a single phosphorylation on CDK12 Thr893. (d) Deconvoluted intact mass spectra for CDK12^715–1038 obtained before and after treatment with recombinant CAK from Candida albicans. The shorter CDK12 construct is essentially unphosphorylated until CAK treatment.