Pathogens employ a variety of mechanisms to exploit the cellular machinery of their hosts to invade and survive. Several bacterial and viral proteins are activated after host cell entry by furin, a host proprotein convertase. The intracellular protozoan parasite Toxoplasma gondii expresses a variety of surface and secretory proteins that are processed by proteases; the role of host furin in this process is yet unclear. In this study, we investigated the potential role played by host furin in the putative processing of particular T. gondii proteins by a comprehensive computational approach. ProP was used to evaluate furin predicted cleavage sites in five proteins (AMA1, ROP11, RON4, GRA21, and MIC8). This was followed by structural modelling, validation, protein–protein docking, molecular dynamics (MD) simulations, and MM-PBSA binding free energy calculations. With good stereochemical quality, favourable TM-scores, and ProSA Z-scores within the range of experimentally determined structures, structural validation verified the accuracy of projected models. Furin and the selected proteins exhibited favourable binding interactions according to docking analysis, which was confirmed by comparison with a negative control, suggesting the specificity of the docking protocol. MIC8 showed greater flexibility, while GRA21, RON4, ROP11, and AMA1 produced relatively stable complexes under simulation conditions. TgRON4 and TgGRA21 displayed the most advantageous binding free energies, followed by TgMIC8 and TgROP11, according to MM-PBSA analysis, but TgAMA1 exhibited unfavourable binding energetics. Overall, these findings may suggest that some T. gondii proteins may be structurally compatible with proteolytic processing. This study should be considered hypothesis-generating and requires experimental validation; it provides computational insights into host-parasite interactions.
Kumari et al. (Wed,) studied this question.