PhrF induced conformational changes disrupt response regulator binding sites.

<p>(A) Side (left) and top view (right) of the superimposition of RapF 3-helix bundle from the PhrF (blue hues) and the ComA (yellow hues) complexes shows that this domain rotates ∼155° as a rigid body using the linker region (dark blue and orange for PhrF and ComA complexes, respectively) as a hinge. As a result of the movement α1 helices of TPR1 motif (cyan and dark red for PhrF and ComA complexes, respectively) superimpose but with inverted orientation, extending from three to five helices the helix bundle in the case of RapF-PhrF complex. (B) RR binding to Rap is impaired in the Phr-induced conformation. Spo0F and DNA-binding domain of ComA (green and yellow surfaces, respectively) were placed in the RapF-PhrF structure by aligning the 3-helix bundle of RapF-Spo0F (3Q15) <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001511#pbio.1001511-Baker1" target="_blank">[6]</a> and RapF-ComA (3ULQ) <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001511#pbio.1001511-Parashar1" target="_blank">[7]</a> with RapF-PhrF structure. RapF-PhrF is represented in ribbon and colored the N-terminal portion in magenta and the TPR domain in blue, view from the side (left) and the top (right).