Fig. 5: The σ⁷⁰-bound putEC structure.

a The cryo-EM map of the σ⁷⁰-bound putEC (3.6 Å) is rendered as semi-transparent surface, colored as labeled, and superimposed with the final σ⁷⁰-bound putEC model. The unexpected RNA hairpin found in the RNA exit channel is zoomed, rotated by ~30°, and re-drawn with the density in a red box. The downstream duplex DNA was not observed in the main channel. Instead, an unknown blob, colored in light brown, was present in the location. b Comparison of the σ⁷⁰-RNAP binding between the RPo and the σ⁷⁰-bound putEC. Nucleic acids were not drawn for clarity. β‘ clamp helices (β‘CH), the main structural element interacting with σ⁷⁰ in the RPo, are highlighted in magenta color. σ⁷⁰ is colored by domains as labeled. β‘-clamp-toe, which interacts with σ_NCR in the σ⁷⁰-bound putEC, is colored green.