Fig. 2

Cryo-EM structure of 21Q-engaged arrested complex. a Nucleic-acid scaffold. Only ordered segment in the structure is shown. Salmon, nontemplate strand; red, template strand; pink, RNA; cyan, QBE subsite 1; green, QBE subsite 2; blue, −10-like sequence. Positions are numbered relative to the transcription start site. b The cryo-EM density map without B-factor sharpening and the superimposed model of 21Q-engaged arrested complex. Gray, RNAP; cyan, Q^I; green, Q^II; yellow, σ⁷⁰; violet, active center Mg²⁺; salmon, nontemplate strand; red, template strand; pink, RNA; blue, −10-like sequence. c The model of 21Q-engaged arrested complex. RNAP and σ⁷⁰ are shown as surfaces. View orientation and colors as in the left subpanel of b. β, except the FTH, is omitted for clarity. d The model of RPo (PDB 4YLN [10.2210/pdb4YLN/pdb]). View orientation and colors as in c, except that the promoter -10 element is colored black