Class I CAP-RNAP-promoter complex EM reconstruction and
fitted model: E. coli species-specific RNAP domains. (A) β′
trigger-loop nonconserved domain (β′GNCD) with β′GNCD
SBHMa domain in orange; β′GNCD SBMHb domain in yellow; β′
trigger loop in green; β′ jaw in blue (stereo pair). (B)
βDR1. (C) βDR2. (D) β residues 1126–1179 (as well as β
N-terminal residues 1–9). (E) σ^70NCR with σ^70NCR insert in
green and 20-residue negatively charged loop that is disordered
in the crystal structure of the σ^70 fragment (32) indicated as
a black dashed line. In each panel, insertion starting and
ending points are indicated by black spheres, the EM map is
contoured at 2.6σ, and other ribbon colors are as in Fig. 2.
Stereo pairs for B–E are shown in Figs. S6 and S7.