Figure 2
Mutations in CDK8 and Conservation of Substituted Residues
(A) Localization of mutations (in red) in a schematic representation of human CDK8 (exon numbering on GenBank: NM_001260.2).
(B) A cartoon of the human CDK8 (based on UniProt: P49336) showing the location of the protein kinase domain (21–335; gray box) and the eight different CDK8 substitutions identified in this work (below, in red). Note that the p.Ser62Leu substitution was identified in five unrelated subjects. Relevant functional elements are depicted in dark boxes. Note the Gly-rich loop (27–35); Lys52, a catalytic residue that interacts with the triphosphate of ATP in the active site; Asp151 within the conserved His-Arg-Asp (HRD) motif (at the catalytic loop), which is directly involved in catalysis; and Asp173, which is included in the Asp-Met-Gly (DMG) motif (at the activation segment) required for chelation of the magnesium ion involved in the catalysis. Substitution of Asp173 is widely used as a catalytically inactive kinase-dead form of CDK8 (p.Asp173Ala).
(C) A multiple-protein sequence alignment of CDK8 and CDK19 at the positions of the identified substitutions in CDK8. Abbreviations are as follows: Hs = human, Mm = mouse, Xt = western clawed frog, Dr = zebrafish, Dm = fruit fly, Ae = yellow fever mosquito, and Ce = nematode worm. The positions of the CDK8 de novo missense variants are indicated with a red arrow at the top of the sequences. Black- or gray-shaded amino acids indicate identical or similar residues compared to the human CDK8 sequence, respectively. Below the alignments, an asterisk (∗) indicates positions that have a single, fully conserved residue, whereas a colon (:) indicates conservation between groups of similar properties. Additional relevant features present in these sequences (Gly-rich loop, DMG motif, and the Asp173 residue, mutated in the kinase-dead mutant) are also depicted.
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