Structural and dynamic characterization of MirA-like xenosiderophore transporters in Fusarium: in silico modeling and in vitro validation.

Fusarium, an omnipresent fungus is known for its pathogenic potential. Pathogenic fungi like all other organisms need iron and are known to produce siderophores for iron acquisition. Siderophore producers possess transporters for their own siderophore as well as for siderophores secreted by other organisms known as xenosiderophore. Although iron is an essential nutrient it can also cause oxidative stress and cell-death at high concentrations. While siderophore utilization is employed by the fungi for efficient iron acquisition, it can be exploited against them by supplying xenosiderophore exogenously in turn increasing iron uptake that might prove lethal. A xenosiderophore-iron transporter MirA has been identified earlier in Aspergillus nidulans for the transport of bacterial siderophore enterobactin. MirA has not yet been identified in Fusarium spp. Present study is a computational analysis that focuses on searching possible orthologs of MirA in Fusarium and predicting its structure using deep-learning-based structural prediction and validation approaches. Docking confirmed binding of predicted Fusarium MiRA transporters with the enterobactin-Fe complex, and the most stable complex was further analyzed by molecular dynamics simulations. RMSD, RMSF, Rg, and SASA analyses demonstrated that interaction with the enterobactin-Fe complex stabilizes the MirA structure, supporting its functional adaptation for siderophore-chelated iron binding. In silico findings are further supported by experimental validation that shows growth inhibitory effect of catecholate siderophore produced by Escherichia coli on Fusarium sp. through anti-fungal plate assay, dry weight estimation and morphological changes through microscopy using LPCB staining. The results suggest possible involvement of MirA in xenosiderophore-mediated biocontrol via siderophore-iron uptake.