Indirect Formation of Peptide Bonds as a Prelude to Ribosomal Transpeptidation

Area of Science:

• Origin of Life Studies
• Biochemistry
• Astrobiology

Background:

• The ribosome's catalytic role in protein synthesis relies on substrate juxtaposition and desolvation.
• Activated aminoacyl esters hydrolyze rapidly and face entropic barriers in bulk water without protection.
• The emergence of a ribosome-like catalyst in the prebiotic era is considered improbable.

Purpose of the Study:

• To investigate alternative mechanisms for prebiotic peptide bond formation in aqueous environments.
• To explore indirect amidation pathways as a precursor to ribosomal peptide synthesis.
• To elucidate the role of specific amino acids in early peptide formation.

Main Methods:

• Utilized fluorine-tagged aminoacyl adenylate esters for synthesis studies.
• Employed in situ ¹⁹F{¹H} NMR spectroscopy for real-time monitoring.
• Conducted kinetic analysis, pH-rate profiling, and temperature-dependence studies.

Main Results:

• Identified indirect amidation via transesterification and O-to-N rearrangement as an efficient peptide formation pathway.
• Demonstrated that serine and threonine, with hydroxyl side chains, play a significant role in this process.
• Resolved ambiguities in previous studies concerning aminolysis reactions in buffer solutions.

Conclusions:

• Indirect amidation offers a viable prebiotic route to peptide synthesis, predating complex ribozymes.
• Specific amino acids, notably serine and threonine, were likely crucial in early peptide evolution.
• This mechanism provides insights into the evolutionary trajectory of protein biosynthesis.