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. 2010 Jul 9;11(9):685–690. doi: 10.1038/embor.2010.96

Figure 3.

Figure 3

A close view of the helix–turn–helix region in oxidized MexR. Magenta, pink, cyan and pale cyan each indicate a promoter. (A) The σA weighted 2Fo–Fc electron density map contoured at 1σ around the disulphide binding between Cys 30 and Cys 62′. (B) Close-up view of superimposition of oxidized MexR and reduced dimer CD showing conformational change around the HTH region before and after MexR oxidation. Atoms are coloured blue (nitrogen), red (oxygen) and yellow (sulphur) and the distance between Cys 30 and Cys 62′ is shown by black dashed lines. After oxidation, the rigid body rotation angle of helix α3′ and the movement of helix α4′ are shown. Key residues surrounding Cys 62′ in dimer CD structure (PDB 1LNW) are labelled. (C) Formation of new interactions in the oxidized MexR. The formation of the disulphide bond between Cys 30 and Cys 62′ is accompanied by newly formed interactions between the HTH motif and helix α1, including the hydrogen bonding of Ser 26 side chain and Gln 60′ backbone carbonyl, Asp 29 side chain and Arg 63′ backbone amide, and a salt bridge between the side chains of Asp 64′ and Arg 70′. HTH, helix–turn–helix.