Origin and evolution of the ribosome

Area of Science:

• Origin of Life
• Molecular Biology
• Biochemistry

Background:

• The modern ribosome's structure and function likely originated before the Last Universal Common Ancestor (LUCA).
• Early ribosome development is hypothesized to stem from the RNA world, involving RNA molecules that evolved into transfer RNAs (tRNAs) and ribosomal RNA (rRNA).
• The peptidyl transferase center within the large rRNA is a key region for understanding early ribosomal function.

Purpose of the Study:

• To infer the likely order of events in pre-LUCA ribosome development.
• To investigate the composition of peptides synthesized by primitive ribosomes.
• To explore the origin and evolution of the genetic code and messenger RNA (mRNA).

Main Methods:

• Inferring the relative age of ribosomal proteins and rRNA regions by analyzing temporally coupled events.
• Examining the properties of modern ribosomes to deduce characteristics of early peptide synthesis.
• Analyzing the structural and functional dynamics of modern ribosomes to hypothesize the emergence of mRNA and coding.

Main Results:

• Primitive ribosomes likely synthesized peptides enriched in l-amino acids, but not exclusively, potentially including d-amino acids.
• The evolution of mRNA as a template for tRNA binding facilitated the development of the genetic code.
• The ribosome's dynamic nature, with tRNA and mRNA movement, is linked to the addition of a template for tRNA binding.

Conclusions:

• Ribosome evolution is deeply rooted in the RNA world, preceding LUCA.
• Early peptide synthesis was not strictly stereospecific, allowing for a mix of amino acid types.
• The development of mRNA as a template was a critical step enabling the genetic code and RNA genomes.