Green, TAP AR2; blue, TAP AR3; orange, RNAP β-flap residues that contact AR2; magenta and light magenta, σR4 and RNAP β-flap-tip residues that contact AR3 (numbered as in TAP and T. thermophilus RNAP holoenzyme and, in parentheses, as in CAP and E. coli RNAP holoenzyme). Other colors as in Fig. 1B-C. Graphs, effects on TAP-dependent transcription of single and double charge-reversal substitutions (mean±SEM; N≥3).
(A) Interactions between AR2, AR3, and RNAP holoenzyme (left, ribbons; right, surfaces).
(B) AR2 interactions.
(C) AR3 interactions.