FIGURE 4.

Amino acid binding studies using ANS fluorescence displacement assays against MtbAldR and its G131T mutant. Concentrations of the amino acid used in each curve are denoted in the insets with different colors. The change in fluorescence intensity was monitored by titrating the MtbAldR-ANS premix against increasing concentrations of aspartate (A), tryptophan (B), tyrosine (C), and alanine (D). The experiments indicate that these amino acids bind to MtbAldR. Binding studies against the G131T mutant were carried out by monitoring the change in the fluorescence intensity after titrating the G131T-ANS premix against increasing concentrations of alanine (E) and leucine (F), respectively. Clearly, the mutant protein cannot bind to the amino acids.