In Silico Evidence for Enterobactin-Facilitated Ferric Iron Import into Mitochondria via ATP Synthase Alpha Subunit Binding

Research on mitochondrial iron metabolism has largely focused on Fe(II), as it is relatively soluble and readily available under physiological conditions. By contrast, the role of Fe(III) remains less well understood. Its poor solubility and tendency to form potentially harmful ferric hydroxides mean that it must remain bound to suitable ligands or chaperones during transport. Canonically, iron is delivered to cells via transferrin (Tf), which binds the transferrin receptor (TfR1) for receptor-mediated endocytosis. Acidification of endosomes releases Fe(III), which is then reduced to Fe(II) by STEAP3 and transported into the cytosol by DMT1, forming a labile iron pool for mitochondrial use. However, the direct trafficking of Fe(III) into mitochondria has remained unexplored. Here, we propose a potential model for Fe(III) uptake into mitochondria through enterobactin, a bacterial siderophore known to influence host iron metabolism. Using in silico docking with AutoDock Vina and AlphaFold2-derived mitochondrial F-type ATP synthase structures, we observe that Fe(III)- enterobactin complexes yield docking scores comparable to Fe(II)-enterobactin complexes at the ATP synthase alpha subunit. In addition, enterobactin itself adopts compatible binding poses at the protein surface. These observations are consistent with a possible interaction framework but do not establish a dissociative mechanism for iron delivery within the mitochondrial matrix. These docking analyses support the structural plausibility of an enterobactin-associated ferric iron interaction with the mitochondrial ATP synthase alpha subunit. Although these findings do not establish a specific transport mechanism, they raise the possibility of an alternative route for mitochondrial iron trafficking. Further experimental work is needed to determine whether this pathway operates in cells and how it contributes to iron homeostasis. More broadly, the proposed model suggests a possible connection between microbial siderophores and mitochondrial iron handling, with potential physiological and pathological relevance.