Rho-dependent transcription termination: mechanisms and roles in bacterial fitness and adaptation to environmental changes

Models of Rho-dependent termination of transcription (RDTT). (A) Diagram of the “catch-up” RDTT model and (B) cryo-EM reconstruction of the “catch-up” pretermination complex (PDBs 8E3F, 8E3H, and 8E6W). (C) Diagram of the “stand-by” RDTT model and (D) cryo-EM reconstruction of the “stand-by” pretermination complex (PDB 6Z9P). Note that the Rho hexamer is in an open, inactive configuration in the “stand-by” complex. To better visualize the orientation of the Rho hexamer relative to RNAP, Rho's NTD and CTD segments are shown in magenta and gray, respectively, in all panels.