Figure 7. Range of clamp conformations for Eco RNAP complexes.

(top) Eσ⁷⁰ is shown as a molecular surface (α, ω, light gray; β, light cyan; β', light pink; σ⁷⁰, light orange) except the clamp/σ⁷⁰₂ module is shown schematically as blue or red outlines (the σ⁷⁰_NCR is omitted for clarity) to illustrate the direction and approximate range for the three major components of the clamp conformational changes (left, opening/closing; middle, twisting; left, rolling). (bottom) Histograms denote the range of clamp conformational changes for Eσ⁷⁰, TraR-Eσ⁷⁰, and rpsT P2-RPo, as indicated. The black bars denote the rotation range defined by dividing the Eigenvalue histograms into three equal bins and determining the clamp position for the red and blue bins (−33 %/+33% bin; see Figure 6). The gray bars denote the estimated rotation range to include 98% of the particles calculated from the Gaussian fits to the Eigenvalue histograms (1% of the particles excluded from each tail; see Figure 6).