FIG 8.

The galE pause sequence and transcription model at the galE–galT cistron junction. (A) Comparison of the G⁻¹⁰-Py⁻¹-G⁺¹ pausing sequences of the galE, his, and mgtA pauses relative to the hairpin formation. The −10, −1, and +1 residues are indicated in red, green, and blue, respectively. (B) Model of a transcription-translation complex, in which RNA polymerase is passing 30 nucleotides downstream from the galE gene (UAA) stop codon while the lead ribosome is terminating translation. (C) Model of a transcription-translation complex, in which RNA polymerase is pausing 130 nucleotides downstream from the galE stop codon while the 30S ribosome of the leading ribosome is still attached to the paused RNA polymerase after the termination of galE translation. Note that in this complex, the transcript RNA (red) is free from the ribosome. (D) Model of a transcription-translation complex in which RNA polymerase is paused 130 nucleotides downstream from the galE stop codon while the leading ribosome 30S subunit forms the preinitiation complex at the galT (AUG) initiation codon. A tRNA is presented over the galT initiation codon to emphasize the translation preinitiation complex. In these models, RNA polymerase is physically connected to the leading ribosome 30S subunit by NusG (dotted dumbbell). (E) Transcription termination model in which the NusG protein brings Rho to the RNA polymerase that is paused 130 nucleotides downstream from the galE stop codon.