High throughput virtual screening reveals a promising specific inhibitor of Toxoplasma gondii N-myristoyl transferase

ALONSO, ANDRÉS; CORVI, MARIA; BUSTOS, DIEGO M

Congreso; Reunión Anual de la Sociedad Argentina de Protozoología; 2014

<!-- @page { margin: 0.79in } P { margin-bottom: 0.08in } --> N-myristoyltransferase (NMT) is a monomeric enzyme that catalyzes the covalent addition of myristate (C14:0 saturated fatty acid) onto proteins. This co- and post-translational modification affects a variety of proteins, many of them important for the life-cycle of cells, and influences different features such as localization, protein-protein interaction and function. Protein myristoylation is essential for cell viability and its peptide recognition sites are species-specific, which makes it an ideal drug target for different pathogens like fungi and protozooan parasites. In this work we performed a bioinformatic analysis that revealed that Toxoplasma gondii genome encodes for a putative NMT which contains the N- and C-terminal domains characteristic of the NMT family. Furthermore, primers designed for the T. gondii NMT coding sequence (CDS) published in the ToxoDB let us determine that NMT is expressed in the T. gondii RH strain. In parallel, a virtual screening (VS) on T. gondii NMT (TgNMT) was performed using over 5000 compounds filtered from the ZINC database. Since the crystal structure of TgNMT is not available, we created a homology model to run the VS. The analysis resulted in 10 compounds with a high predicted inhibition constant (Ki) over TgNMT, but only one of them was more specific for TgNMT than that of the host NMT (hNMT). Interaction analysis of the compound with TgNMT allowed us to infer that this compound might interact with the peptide binding site of the enzyme, a site that has been described to be species-specific. Besides, the compound interacts with the myristoil-CoA binding site of the hNMT, which is conserved along different species, but the interaction of the compound with hNMT was found to be a hundred times lower than with TgNMT. These preliminary results are the first report on specific TgNMT inhibitors and the starting point for the study of treatments designed specifically for toxoplasmosis.