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. Author manuscript; available in PMC: 2012 Apr 1.
Published in final edited form as: J Mol Biol. 2010 Dec 31;407(3):333–353. doi: 10.1016/j.jmb.2010.12.037

Figure 3.

Figure 3

Genetic epistasis experiments between single base pair substitutions of the soxbox of the zwf promoter and DNA binding mutants of SoxS. The sequence of the non-template strand of the zwf soxbox is shown in panel C; the invariant A of the soxbox is at the 5' end of the sequence. (A) (Left) Epistatic interaction between the R40A substitution in the N-terminal HTH motif of SoxS and base pair substitution G4A of RE 1. (Right) Non-epistatic interaction between the Q39A substitution in the N-terminal HTH motif of SoxS and substitution C7T of RE 1. (B) (Left) Epistatic interaction between the T87A substitution in the C-terminal HTH motif of SoxS and base pair substitution A17C of RE 1. (Right) Epistatic interaction between the R90A substitution of the C-terminal HTH motif of SoxS and substitution T15G of RE 2. (C) A schematic representation of the interactions between amino acid residues of SoxS and nucleotide bases within the zwf soxbox, as determined by the genetic epistasis tests shown in (A) and (B). The epistasis data show that amino acids of the N- and C-terminal HTH motifs of SoxS each contact one base pair within RE 1 and RE 2, respectively, but whether the contacted base is on the template or non-template strand cannot be determined by these tests.