Biomolecular Mechanisms of Iron Oxidation in prokaryotes: a protein focused review

Iron oxidation by prokaryotes is a fundamental biogeochemical process with broad environmental and biotechnological significance. Despite growing knowledge of iron oxidation pathways at the systems level, the structural and biochemical characterization of individual proteins directly responsible for ferrous iron [Fe(II)] oxidation remains limited. This review provides a critical survey of the molecular knowledge of proteins directly involved in Fe(II) oxidation across phylogenetically diverse microorganisms (including acidophilic bacteria and archaea and neutrophilic bacteria) spanning aerobic, anaerobic, and phototrophic metabolic strategies. For each protein (Cyc2, Cyt572, Cyc2PV-1, sulfocyanin, FoxC, PioAB complex, MtoAB complex, and Iro), we discuss structural features, cofactor binding and localization, and redox properties, integrating experimental biochemistry with structural predictions. We further provide an overview of how broader computational approaches, including molecular dynamics simulations and quantum methods, also for redox potential calculations, can complement experimental data to yield mechanistic insights into iron oxidation. Finally, we highlight existing knowledge gaps and outline biotechnological applications (including bioleaching, wastewater treatment, bioremediation, and bioelectrocatalysis) that stand to benefit from a deeper molecular understanding of these proteins.