Triple Mycobacterial ATP-synthase mutations impedes Bedaquiline binding: Atomistic and structural perspectives.

Bedaquiline (BDQ) has demonstrated formidable bactericidal activity towards Mycobacterium tuberculosis (Mtb) in the treatment of multi-drug resistant (MDR) and extensively drug resistant (XDR) tuberculosis (TB). BDQ elicits its therapeutic function by halting the ionic shuttle of Mtb via mycobacterial FF ATP-synthase blockade. However, triple mutations (L59 V, E61D and I66 M) at the ligand-binding cavity characterize emerging BDQ-resistant strains thereby restraining the potentials embedded in this anti-microbial compound, particularly in MDR/XDR-TB therapy. In this report, the effects of these triple mutations on BDQ-Mtb FF ATP-synthase binding were investigated using molecular dynamics, free energy binding and residue interaction network (RIN) analyses. The highlight of our findings is the drastic reduction in BDQ binding affinity (ΔG) in the triple mutant protein, which was caused by a systemic loss in high-affinity interactions primarily mediated by L59, E61 and I66. While wildtype L59 and I66 formed pi-alkyl interactions with BDQ at the FF ATP-synthase binding site, E61 elicited conventional (O--HO) bond. Upon transition, V59 and I66 were devoid of interactions with BDQ while D61 existed in a weaker non-conventional (C--HO) bond. Likewise, these mutations distorted the binding site and overall structural architecture of FF ATP-synthase in the presence of BDQ as revealed by the RIN and conformational analyses. Insights from this study could serve as a starting point for the structure-based design of novel inhibitors that could overcome mutational setbacks posed by BDQ-resistant strains in MDR/XDR-TB treatment.