Structure-Activity Relationships in Nonenzymatic Template-Directed RNA Synthesis

Area of Science:

• Biochemistry
• Origin of Life Studies
• Molecular Biology

Background:

• Template-directed RNA synthesis is crucial for understanding the transition from prebiotic chemistry to early life.
• The precise chemical mechanisms governing RNA replication remain incompletely understood.

Purpose of the Study:

• To elucidate the mechanism of RNA copying by examining the kinetics of template-directed synthesis.
• To investigate the role of modified 3'-nucleotides in RNA replication.

Main Methods:

• Kinetic measurements of template copying using primers with modified 3'-nucleotides.
• Determination of crystal structures of modified nucleotides within primer/template/substrate-analog complexes.
• Analysis of pH-rate profiles and solvent isotope effects.

Main Results:

• Deprotonation of the primer 3'-hydroxyl precedes the rate-limiting step of phosphodiester bond formation.
• RNA analogs exhibiting a ³E ribose conformation demonstrated the fastest phosphodiester bond formation.
• Reaction rates correlated strongly with the electronegativity of the 2'-substituent on the ribose.

Conclusions:

• The study provides mechanistic insights into RNA copying, highlighting the importance of primer 3'-hydroxyl deprotonation and the 2'-substituent's electronic properties.
• Differences in steric bulk and charge distribution between ground and transition states influence RNA synthesis efficiency.
• Findings contribute to understanding the chemical basis for the emergence of RNA-based life.