Prebiotic iron-sulfur peptide catalysts generate a pH gradient across model membranes of late protocells

Prebiotic chemistry was likely mediated by metals, but how such prebiotic chemistry progressed into the metabolic-like networks needed to sustain life remains unclear. Here we experimentally delineate a potential path from prebiotically plausible iron-sulfur peptide catalysts to the types of pH gradients exploited by all known living organisms. Iron-sulfur peptides cooperatively accept electrons from NADH in a manner that is only partially mediated by ionic interactions. The electrons are then either passed to a terminal electron acceptor, such as hydrogen peroxide, or to an intermediate carrier, such as ubiquinone. The reduction of hydrogen peroxide leads to the production of hydroxide, which then contributes to the formation of a pH gradient across late protocell membranes. The data are consistent with the activity of prebiotic iron-sulfur peptide catalysts providing a selective advantage by equipping protocells with a pathway that connects catabolism to anabolism.