Multiple prebiotic metals mediate translation.

Today, Mg is an essential cofactor with diverse structural and functional roles in life's oldest macromolecular machine, the translation system. We tested whether ancient Earth conditions (low O, high Fe, and high Mn) can revert the ribosome to a functional ancestral state. First, SHAPE (selective 2'-hydroxyl acylation analyzed by primer extension) was used to compare the effect of Mg, Fe, and Mn on the tertiary structure of rRNA. Then, we used in vitro translation reactions to test whether Fe or Mn could mediate protein production, and quantified ribosomal metal content. We found that () Mg, Fe, and Mn had strikingly similar effects on rRNA folding; () Fe and Mn can replace Mg as the dominant divalent cation during translation of mRNA to functional protein; and () Fe and Mn associate extensively with the ribosome. Given that the translation system originated and matured when Fe and Mn were abundant, these findings suggest that Fe and Mn played a role in early ribosomal evolution.