Identification and Validation of Novel Inhibitor Against Chorismate Synthase of Toxoplasma Gondii
Posted: 13 Feb 2020 Last revised: 20 Feb 2020
Date Written: February 11, 2020
Toxoplasmosis is caused by an apicomplexan parasite Toxoplasma gondii that enter in the human body through the intake of food and water contaminated with oocyst. Worldwide prevalence of toxoplasmosis was reported about 25-30% in the human population particularly in Latin America and tropical African countries. The factors reported for the increment of prevalence rate generally includes environment, socio-economic, and quality of water. Due to emerging resistant against current chemotherapy, there is an emerging need for developing and finding new and specific therapeutics for this disease. The shikimate pathway provides basic building blocks for a variety of aromatic compounds. As it is absent in humans, the enzymes of the shikimate pathway are attractive targets for antimicrobial drug development and inhibition of the pathway is effective in controlling growth of several bacterial species. In the present study, amino acid sequence of T. gondii chorismate synthase (TgCS) was retrieved from ToxoDB and alignment was performed using PSI-BLAST. Comparative modelling of was carried out with ITASER following by refinement with ModRefiner and ModLoop. Autodock vina was used for the docking study of FMN and EPSP with modelled structure of TgCS. For the analysis of structural stability and dynamics, 50ns MD was done for apo, binary and ternary structures. The stability and flexibility in trajectories had been checked by RMSD, RMSF, and Rg.
Three dimensional structure of TgCS was generated using HpCS (1UM0) as a template. Comparative sequence and structural analysis of TgCS was carried out against HpCS (1UM0) and SpCS (1QXO), which revealed the conservation of three signature motifs of chorismate synthase and presence of core forming Beta-Alpha-Beta sandwich fold, and also conservation of the binding site residues for the FMN and EPSP. For docking analysis, 1QXO (co-crystallized FMN and EPSP) was used to determine the FMN and EPSP confirmation in the active site of TgCS. Molecular dynamics showed the presence of EPSP with FMN stabilises the protein more than the binary complex (protein and FMN). The RMSF represents that the active site residues in the ternary complex is getting more stabilised than the apo and binary complex of TgCS. Furthermore, virtual screening is being carried out by screening substructures of reported drug compound and the analogs of substrate. Our study provides the structural insights into the TgCS and will be helpful in identifying potent lead compounds that can be further used for the drug designing against toxoplasmosis.
Keywords: Comparative modelling, Model refinement, Docking, Simulation, Virtual screening
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