Structural Mechanisms Driving the Selective Efficacy of Oxamniquine against Schistosoma mansoni and Schistosoma japonicum

Oxamniquine (OXA) exhibits selective efficacy against different Schistosoma species, with the highest activity observed in Schistosoma mansoni sulfotransferase (SmSULT) and the lowest in Schistosoma japonicum sulfotransferase (SjSULT). This study utilises advanced atomistic and molecular simulations to elucidate the structural dynamics induced by OXA binding to SmSULT and SjSULT, aiming to unravel the underpinnings of this selective efficacy. Binding free energy (BFE) analyses revealed a markedly higher affinity of OXA for SmSULT (-48.04 kcal/mol) compared to wtSjSULT (-22.84 kcal/mol), with a significant restoration of binding affinity (-39.23 kcal/mol) observed in SjSULT following the mutation of Val139 to Gly139. Comprehensive conformational assessments highlighted that SmSULT-OXA achieves its superior efficacy by stabilising the protein structure, in stark contrast to the erratic conformational behaviour of wild-type SjSULT. Notably, this erratic behaviour is ameliorated upon mutation, leading to a restoration of OXA's efficacy in SjSULT. These insights elucidate the structural mechanisms underpinning OXA's selective efficacy and provide valuable perspectives on its targeted action against Schistosoma spp.