Optimization of phage heptapeptide library-screening process for developing inhibitors of the isocitrate lyase homologue from Mycobacterium tuberculosis

The aims of this study were to screen peptide inhibitors specific for isocitrate lyase (ICL) using a phage peptide library and computer molecular docking and to explore the relevant mechanisms. Using ICL as a target, the phage peptide library was screened to obtain peptides with specific binding affinity. Based on the three-dimensional crystal structure of ICL(pdb:1F8I), the obtained polypeptides were docked to the 1F8I using the computer-simulated molecular docking technique. The successfully docked polypeptides were synthesized using the Fmoc solid-phase synthesis method, and the ICL inhibition rate of these peptides was measured. Finally, the possible mechanism underlying the inhibition was explored by Binding Site Analysis. A total of 29 heptapeptides were obtained through screening the phage peptide library. We found that 12 out of the 29 peptides were successfully docked to the 1F8I, and all 12 peptides could obviously inhibit the ICL activity, of which three heptapeptides showed an inhibiting (extent of inhibition over 50 %), IC50 value of 126 μM. Structural analysis revealed that the ICL tetramer has a large cavity in the center, and the polypeptides bind to ICL at amino acid residue 119’s GLN of the ICL monomer. We successfully obtained peptide inhibitors specific for ICL, and analyzed the mechanism underlying the interaction between the peptides and ICL. Our study provides scientific evidence for the development of antituberculosis peptide drugs targeting ICL.