Figure 1.

Chemical structures of (A) tricin and (B) flavopiridol. Docking poses of (C) tricin and (D) flavopiridol in the binding site of CDK9. In (A) and (B), the definitions of the rings, that is, A–C for tricin and A–D for flavopiridol, are also shown. In (C) and (D), the brown ribbon represents the backbone structure of CDK9. In (C), the OH groups in the A‐ and B‐ring of tricin are directed toward Asp167 and Cys106, respectively. In (D), the D‐ring of flavopiridol is located close to Asp167, and the carbonyl oxygen of the C‐ring is directed toward Cys106.