Complex of human CDK13 (cyclin dependent kinase 13) and human cyclin K. The proteins were co-expressed in Sf9 insect cells along with S. cerevisiae CAK1 (Serine/threonine-protein kinase CAK1).

Recombinant human CDK13, encompassing amino acids 516-1512 (end), contains an N-terminal GST-tag. Recombinant human Cyclin K, full length encompassing amino acids 1-580 (end), also contains an N-terminal GST-tag. Recombinant S. cerevisiae CAK1, encompassing amino acids 2-368 (end), contains a FLAG-tag. The proteins were purified using the GST tags.