FIG 5.

M. tuberculosis TrpE amino acid sequence, Trp binding site motifs, and location of IPA–fluoro-anthranilate double-resistant missense mutations. (A) Amino acid sequence of the N-terminal half of TrpE. The allosteric Trp binding motif LLESX₁₀S is indicated by the gray background. Residues involved directly in subunit association are underlined. Arg65 in the X₁₀ loop of the Trp allosteric binding motif, forming a hydrogen bond with His170, is marked by a blue arrow. Positions of the IPA and fluoro-anthranilate double-resistance mutations identified in this work are indicated in red. The Phe68Ile mutation site identified by Zhang et al. is indicated in green (12). (B) View of the TrpE dimer interface. The two monomers are colored yellow and orange, respectively. Hydrogen bonds are shown as black dashed lines. The amino groups of His170/His170′ form hydrogen bonds with the carbonyl groups of Arg65/Arg65′ (the N···O distance is 2.81 Å). His170 and His170′ interact via pi-pi stacking. Structure and motif annotations are according to Bashiri and colleagues (15). (C) Location and nature of IPA–fluoro-anthranilate double-resistance-conferring missense mutations. *, mutants were selected on fluoro-anthranilate-containing agar. Other mutants were selected on IPA-containing agar. #, mutations identified in M. bovis BCG. Other mutations were derived from M. tuberculosis. The TrpE amino acid sequences of M. bovis BCG and M. tuberculosis are identical.