GTP before ATP: The energy currency at the origin of genes

TL;DR

This paper explores the evolutionary origins of cellular energy currencies, proposing GTP as the ancestral molecule before ATP, and discusses how early metabolism was driven by H2-dependent CO2 reduction.

Contribution

It introduces the hypothesis that GTP was the original energy currency prior to ATP and links early metabolic processes to transition metal catalysis in LUCA.

Findings

GTP was likely the first energy currency in early life.

ATP synthase evolved after the ribosome and GTP use.

Early metabolism was driven by H2-dependent CO2 reduction.

Abstract

Life is an exergonic chemical reaction. Many individual reactions in metabolism entail slightly endergonic steps that are coupled to free energy release, typically as ATP hydrolysis, in order to go forward. ATP is almost always supplied by the rotor-stator ATP synthase, which harnesses chemiosmotic ion gradients. Because the ATP synthase is a protein, it arose after the ribosome did. What was the energy currency of metabolism before the origin of the ATP synthase and how (and why) did ATP come to be the universal energy currency? About 27% of a cell's energy budget is consumed as GTP during translation. The universality of GTP-dependence in ribosome function indicates that GTP was the ancestral energy currency of protein synthesis. The use of GTP in translation and ATP in small molecule synthesis are conserved across all lineages, representing energetic compartments that arose in the last universal common ancestor, LUCA. And what came before GTP? Recent findings indicate that the energy supporting the origin of LUCA's metabolism stemmed from H2-dependent CO2 reduction along routes that strongly resemble the reactions and transition metal catalysts of the acetyl-CoA pathway.