Folding and Catalysis Near Life’s Origin: Support for Fe2+ as a Dominant Divalent Cation

Abstract

There is broad consensus that during and immediately following the origin of life, RNA was the single biopolymer or was among a small group of cooperating biopolymers. During the origin of life, the Archean Earth was anoxic; Fe2+ was abundant and relatively benign. We hypothesize that RNA used Fe2+ as a cofactor instead of, or along with, Mg2+ during the inception and early phases of biology, until the Great Oxidation Event (GOE). In this model, RNA participated in a metal substitution during the GOE, whereby Mg2+ replaced Fe2+ as the dominant RNA cofactor. A GOE-induced Fe2+ to Mg2+ substitution predicts that under ‘early Earth’ (anoxic) conditions, Fe2+ can participate in a variety of functions, including mediation of RNA folding and catalysis by ribozymes and proteins. Understanding the influence of Fe2+ on nucleic acid structure and function could provide an important link between the geological record and the ancestral biological world. This review focuses on experimental work investigating the interactions and func- tions of RNA and nucleic acid processing proteins with Fe2+ under anoxic, early Earth conditions.