Evidence supporting the reliability of LeuBAT complexes

In order to prove that the LeuBAT complexes are reliable models for BAT-inhibitor complexes, it is necessary to find out the correlation between key residues in the primary binding site of Δ13 LeuBAT  and key residues of BATt. Mutations in subsite A (Y21A, D24E and S355T) and in subsite B (F259T)  in the context of the Δ13 LeuBAT construct were prepared and analysed. Mutants' [3H] sertraline Kd values were measured and log Kd was plotted against log Ki of the homologous human SERT mutants (figure 7). There is a linear relationship between the mutants in LeuBAT and that of SERT. This means that the mutants in LeuBAT have similar effects to those in SERT, and LeuBAT offers a framework for understanding the pharmacological properties of SERT. In addition, all human BATs were compared with the pharmacological selectivity of LeuBAT through plotting log Ki (LeuBAT) versus log Ki (human dopamine transporter (DAT), NET or SERT) (figure 8). They all showed a linear relationship with mutants of LeuBAT to various degrees. This suggests that the pharmacological properties of LeuBAT are a hybrid of human BATs. 

Figure 7. Plot of sertraline binding constants for Y21A, D24E, F259Y and S355T mutants of the D13 LeuBAT against the inhibition constants for the corresponding mutants Y95A, D98E, F341Y and S438T in SERT, respectively. WT, wild type. (Wang, Hui 2013)

Figure 8. Comparison of pharmacology selectivity of LeuBAT with human dopamine transporter (hDAT), human serotonin transporter (hSERT) and human noradrenaline transporter (hNET). (a) Plot of drugs inhibition constants for hDAT against inhibition constants for Δ13 LeuBAT. The R2 (goodness-of-fit of linear regression) value is 0.78. (b) Plot of drugs inhibition constants for hSERT against inhibition constants for Δ13 LeuBAT. The R2 (goodness-of-fit of linear regression) value is 0.14, but the R2 would be 0.71 if the mazindol point is left out. (c) Plot of drugs inhibition constants for hNET against inhibition constants for Δ13 LeuBAT. The R2 value is 0.16, but the R2 would be 0.50 if the sertraline point is left out. (Wang, Hui 2013)