2026-06-10 カリフォルニア大学サンディエゴ校（UCSD）
＜関連情報＞
- https://today.ucsd.edu/story/what-powered-the-earths-earliest-life
- https://www.pnas.org/doi/10.1073/pnas.2520997123
GTP代謝回転率が増加したGTP合成酵素リボザイム A GTP synthase ribozyme with increased GTP turnover
Xu Han, Zoe J. Pepper, Joshua T. Arriola, and Ulrich F. Müller
Proceedings of the National Academy of Sciences Published:June 9, 2026
DOI:https://doi.org/10.1073/pnas.2520997123
Significance
An early stage of life must have used catalytic RNAs (ribozymes) to self-replicate in a prebiotic environment. Self-replication would have required RNA polymerization from chemically activated nucleotides, which exist in today’s biology as nucleoside 5′-triphosphates (NTPs). We previously developed a ribozyme that is able to synthesize guanosine 5′-triphosphate (GTP) by metabolic coupling between two ribozymes in emulsion droplets. Here, we improved the GTP turnover of this ribozyme by selection in emulsion from a library of ribozyme variants. The resulting ribozyme had a GTP turnover of about 13, and a coupled reaction with an RNA polymerase ribozyme led to the incorporation of five guanosines into an RNA polymer. This represents an important step toward recapitulating an early RNA-dominated stage of life in the lab.
Abstract
Before the invention of encoded protein translation, early stages of life likely relied on catalytic RNAs (ribozymes). To test how such a system could have functioned, researchers have developed ribozymes that could have provided central functions. The central function of self-replication would have required templated RNA polymerization of nucleotides, which is energetically driven in today’s life forms by the use of nucleoside 5′-triphosphates (NTPs). We previously showed that ribozymes can catalyze the formation of guanosine 5′-triphosphate (GTP) from guanosine and the prebiotically plausible polyphosphorylation reagent cyclic trimetaphosphate (cTmp) by generating a guanosine triphosphorylation ribozyme (GTR) using an in vitro selection in emulsion. This ribozyme (GTR1) had a catalytic rate enhancement of about 18,000-fold but a turnover of only about 1.7. Here, we improved this ribozyme by emulsion selection from a doped library of GTR1 that was metabolically coupled to a polymerase ribozyme. High-throughput sequencing and biochemical analysis identified the most efficient variant of GTR1 with 19 mutations, which increased the GTP turnover number to ~13. Biochemical analysis of this GTR1e revealed biphasic reaction kinetics with an apparent overall KMAPP around 11 mM for cTmp. When coupled to an RNA polymerase ribozyme, up to five guanosines were incorporated into an RNA polymer, which represents an important step toward modeling an RNA-based life form in the lab.
