Fig. 5: Potential mismatched dB:UTP base pair configuration within E. coli RNAP active site.

a Surface representation of dB:UTP observed in our cryo-EM structure. b A dB:UTP wobble base pair model was prepared based on a G:U wobble base pair (PDB 6L0Y). c A dB:UTP reverse wobble base pair was modeled based on a Bt1-T reverse wobble base pair27. The i + 1 base pair and minor-groove edge contacting loop are highlighted in surface view. Other color code is the same as Figs. 2 and 3.