Fig. 1. (A) Crystallographic structure of the ChrR–σE complex (pdb ; 2Z2S)8 showing the sigma factor σE in orange and the anti-sigma factor ChrR in blue with anti-sigma factor domain in dark blue and cupin-like domain in light blue. The zinc ion is shown in magenta. (B) View of the anti-sigma factor domain zinc finger site embedded within helices H1, H2 and H3, showing Zn2+-binding histidines and cysteines of the H–X24–H–X3–C–X2–C motif.
