Iron, immunity, and infection
© 2018 by Taylor & Francis Group, LLC. Iron is a highly abundant element and plays a critical role in basic physiological processes across almost all life-forms. The ability of iron to transition between its ferrous (Fe2+) and ferric (Fe3+) valency states, along with its capacity to form multiple chemical bonds in various orientations, imbues it with properties that are useful to catalyze biochemical reactions and transfer electrons. Iron plays a key role in generation of energy as the binder of oxygen in heme and as a component of the mitochondrial electron transport chain that generates ATP from oxygen by means of oxidative phosphorylation (Hate 1985). Furthermore, iron-dependent enzymes play many other important roles in cellular metabolism and macromolecular biogenesis, especially with respect to DNA (Zhang 2014), a key exemplar being ribonucleotide reductase, the enzyme responsible for the rate-limiting step in DNA synthesis (Jordan and Reichard 1998). Where iron is present in proteins, it is often as part of an iron-sulphur complex (Maio and Rouault 2015). Indeed, one explanation for the near-universal dependency of life-forms on iron is that the origins of life have an iron-sulphur-related basis. This “iron-sulphur world” hypothesis put forward by Günter Wächtershäuser posits that early life began autotrophically (Wächtershäuser 1992) in a volcanic hydrothermal ow at high pressure and temperature, such as in undersea hydrothermal vents, which can contain “micro-caverns” with walls of iron sulde. Synthetic reactions involving hydrogen sulde, water, and carbon monoxide in the presence of iron sulde are believed to have generated early building blocks of biochemical molecules (Keller et al. 1994; Huber and Wachtershauser 1998; Cody et al. 2000). The theory holds that the Last Universal Common Ancestor may have emerged in hydrothermal vents-potentially explaining the near-universal presence of iron and.