FIGURE 1.

The interaction of σ⁷⁰ H5 with the β-flap tip is disrupted by AsiA. A, structure of T. thermophilus RNAP (2) (Protein Data Bank code 1IW7) shows the interaction between σ H5 and the β-flap tip. σ is shown in blue; β is shown in orange, and the remainder of core is shown in gray. B, schematic shows how the interaction of the β-flap (β-F; orange circle) with Region 4 of σ⁷⁰ (blue) in RNAP (left panel) is remodeled by the T4 proteins AsiA (red) and MotA (green) (right panel). The remodeled σ Region 4 is no longer able to interact with the −35 element or the β-flap, and MotA interacts with the −30 region of the promoter DNA, the MotA box. Other interactions between σ⁷⁰ Region 2 and the −10 element and Region 3 and the DNA are retained.