Figure 1.

Schematic of experimental strategy used to monitor the transcription bubble conformation. (A) Fluorophore positions on a cut-away structural model of Escherichia coli RP_O obtained using accessible volume modelling (see ‘Materials and Methods’ section). σ⁷⁰ is shown in orange and core protein is shown in grey except for the regions that protrude in front of the cut-away plane, which are yellow. The β subunit is omitted for clarity. The template strand is shown in blue, the non-template strand in teal. The active site Mg²⁺ ion is shown as a pink sphere. (B) Schematic of experimental immobilization approach. RP_O is immobilized on a PEG-coated surface via anti-His₅/His₆-tag interactions.