Mg2+ is essential for RNA folding and catalysis. However, for the first 1.5 billion years of life on Earth RNA inhabited an anoxic Earth with abundant and benign Fe2+. We hypothesize that Fe2+ was an RNA cofactor when iron was abundant, and was substantially replaced by Mg 2+ during a period known as the 'great oxidation', brought on by photosynthesis. Here, we demonstrate that reversing this putative metal substitution in an anoxic environment, by removing Mg2+ and replacing it with Fe2+, expands the catalytic repertoire of RNA. Fe 2+ can confer on some RNAs a previously uncharacterized ability to catalyse single-electron transfer. We propose that RNA function, in analogy with protein function, can be understood fully only in the context of association with a range of possible metals. The catalysis of electron transfer, requisite for metabolic activity, may have been attenuated in RNA by photosynthesis and the rise of O2.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)