Abstract

Introduction: Tuberculosis has been studied as a potentially serious bacterial infection affecting the lung caused by Mycobacterium tuberculosis. In addition to its severe impact on health, resistance to existing drugs has also been seen as a rising concern in the space of medicinal solutions. Therapeutic peptides have the potential to complement existing drug designs to provide effective outcomes against Mycobacterium tuberculosis-resistant strains.

Methods: This study illustrated a computational approach to design and test peptides against NADHdependent enoyl-acyl carrier protein reductase of Mycobacterium tuberculosis. A human antimicrobial peptide LL-37 was used as a template, and a further 6 peptides were designed, and their binding and interactions against NADH-dependent enoyl-acyl carrier protein reductase were examined. Further, toxicity, immunogenicity, and a broad spectrum of physicochemical properties were calculated to evaluate the therapeutic and safety profile of these peptides.

Results: These peptides were structurally modelled and docked with the protein to determine their binding poses and affinity. The molecular interaction of LL-37 with protein was treated as a reference to evaluate the effectiveness of designed peptides. Solvent accessible surface area (SASA) and ΔG binding free energy of docked complexes assisted in the ranking of these peptides. Eventually, peptides P1: LLGDFFRKSKEK, P3: LLFGDRFLLKEK and P7: LLGDFFRLLKEK were selected for 100 ns molecular dynamic simulation as they showed predicted dissociation constants of 8.7×10-4 M, 3.3×10-4 M and 1.2×10-4 M, respectively. These peptides showed direct hydrogen bond formation with ILE21 and LYS165, which are critical active site residues of the protein. The structural variation pattern collected from the MD simulation suggested a strong and stable binding of P3 and P1 with the protein with RMSD 4-5 Å with the starting conformation under the non-fluctuating state. These two peptides showed relatively similar binding results compared with the control peptide LL-37. Comprehensive structural analysis was performed for the middle structures of the most populated cluster generated from 100 ns MD simulation trajectory.

Conclusion: Later, MMPBSA binding energies of these structures were computed, where the average binding free energies of P1, P3, and P7 peptides were -146.93 kcal/mole, -161.16 kcal/mole, and - 151.44 kcal/mole, respectively. These energies suggested that P3 is strongly bound to the active site of NADH-dependent enoyl-acyl carrier protein reductase. Overall, this study proposed the application of these peptides as a possible therapeutic solution to inhibit the growth of Mycobacterium tuberculosis.