Fig. 1. Crystal structure of FasR_Δ33-C₂₀-CoA.

a FasR dimer in cartoon representation, the two protomers are distinguished in light blue and pale green. The dimer is strictly symmetric, with one protomer in the asymmetric unit, the crystallographic twofold is depicted as a vertical axis in the plane of the figure. Secondary structure elements are labelled; a prime symbol denotes equivalent elements in the other protomer. The two domains are indicated, an N-terminal DNA-binding domain with a helix–turn-helix (HTH) motif, and a C-terminal domain with the co-crystallised effector molecule C₂₀-CoA bound (in spheres coloured by element). b Details of the effector-binding tunnel. Three orthogonal views illustrate the molecular surface of FasR_Δ33.The leftmost cuts along the middle of a protomer, revealing the top tunnel mouth on the right and a large segment of the tunnel itself with the bound acyl moiety (in sticks). A few amino acid side chains that define the tunnel walls are labelled. The rightmost panel is an open-book perspective, with the footprint of protomer A visible on protomer B’s surface (in pale green), the two openings of the tunnel are visible, showing solvent exposure of both tips of the C₂₀-CoA molecule.