Rational design of potential Shiga toxin type 2 inhibitors by virtual screening

DAIANA GIOIA; CASAL, JUAN J.; RICARDO A. DORR; ROXANA TORIANO

Congreso; SAFIS + ALACF JOINT MEETING 2021. Argentine Society of Physiology and Latin American Association of Physiological Sciences; 2021

Argentine Society of Physiology and Latin American Association of Physiological Sciences

Shiga toxin (Stx) is known as one of the most potent bacterial toxins. It is present in the group of "Shiga toxin-producing E. coli" (STEC) which contains the genes for Stx1 and Stx2. STEC is one of the most important emerging pathogens of foodborne infections. Human STEC infection reveals in a broad clinical spectrum whose most severe manifestation is Hemolytic Uremic Syndrome (HUS) which is associated with Stx2 and which still has no specific treatment. Stxs are AB5 toxin type consisting of a monomeric, enzymatically active A subunit non-covalently linked to a pentameric B subunit responsible for binding to the globotriaosylceramide (Gb3), a specific receptor on the cell surface. The A subunit enters the target cell where it injures the eukaryotic ribosome, arresting protein synthesis. The aim of this work is to identify small molecules that block the RNA-N-glycosidase activity of subunit A and thus prevent ribo-toxic activity. The strategy used and the preliminary results were: i) starting from the structure of the crystallized protein (PDB Stx2-1R4P) and through FPOCKET software, one "druggable pocket" was selected from 20 detected; ii) using FDA and Maybridge Hitfinder compound libraries (20000 compounds), virtual screening (VS) was performed; iii) using molecular docking techniques, an affinity study between those compounds and crystallized Stx2 was carried out and 10 compounds (hits) were selected; iv) the complexes with the best scoring and favorable interactions were selected and regrouped in clusters considering both lipophilic properties and structural diversity; v) using molecular dynamics (MD) calculations, the temporal stability of the ligand-Stx2 complexes and their binding energy were studied. In conclusion, from the combination of VS and MD techniques, a series of structurally diverse compounds with potential anti-Stx2A activity was identified. In the future, structural modification of the hits will allow us to improve their pharmacodynamic and pharmacokinetic profiles.