σ appropriation at a T4 middle promoter. Cartoon depicting a model of RPo at a T4 middle promoter (colors as in Fig. 1). Interaction of AsiA with σ70 Region 4 remodels Region 4, preventing its interaction with the β-flap or with the -35 region of the DNA. This interaction then facilitates the interaction of MotANTD with σ70 H5 and MotACTD with the MotA box centered at -30. Protein-DNA interactions at σ70 promoter elements downstream of the MotA box (the TGn and -10 elements) are not significantly affected. ADP-ribosylation of Arg265 on each α-CTD, catalyzed by the T4 Alt and ModA proteins, is denoted by the asterisks. The modification prevents the α subunits from interacting with DNA upstream of the MotA box.