Figure 7: Comparison of effector-mediated conformational changes between V. cholerae and E. coli.

(a) The VcFadR–DNA complex. The linker helix α4 is red and changes to a loop in the VcFadR–ligand complex (b). α4 from chain B is distinguished by a prime. (c) Superposition of the structures of the VcFadR–DNA complex and VcFadR–ligand complex. The DNA-binding domain is in magenta (VcFadR–DNA complex) or cyan (VcFadR–ligand complex) and the rest of the protein is white. The arrows show that, upon ligand binding, the DNA-binding domain is widened to almost 180°. Residues from chain B are distinguished by a prime following the amino-acid number. (d) Superposition of the structures of EcFadR–DNA complex (PDB 1H9T)¹⁷ and EcFadR–ligand complex (PDB 1H9G)¹⁷. The DNA-binding domain is magenta (EcFadR–DNA complex) or green (EcFadR–ligand complex) and the rest of the protein is white.