Fig 3. Cryo-EM reconstruction of the class-II CAP-TAC with de novo RNA transcript.

(A) Overview of the cryo-EM reconstruction map of the E. coli class-II CAP-TAC with RNA transcript at 4.4 Å resolution and the state 2 architecture. The color schemes for the split density maps (8 RMS) and the docked components are same as in Fig 1. (B) A close-up view of the promoter DNA scaffold in the complex. The insert is the zoom-in view of the DNA-RNA hybrid region with the magenta Mg²⁺ sphere. A de novo synthesized RNA transcript (3-nucleotide) starting from the −1 position with a GTP residue is displayed. CAP-TAC, CAP-dependent transcription activation complex; cryo-EM, cryo–electron microscopy; NCR, non-conserved region; RMS, root-mean-square.