Origin of the 16S Ribosomal Molecule from Ancestor tRNAs

Area of Science:

• Evolutionary biology
• Molecular biology
• Origin of life

Background:

• The origin of ribosomal RNA (rRNA) and ribosomal subunits is a key question in understanding the early evolution of life.
• Transfer RNA (tRNA) molecules are fundamental to protein synthesis and have ancient origins.

Purpose of the Study:

• To test the hypothesis that concatemers of ancestral tRNAs gave rise to the 16S ribosomal RNA.
• To explore the potential role of proto-tRNAs in the formation of the small ribosomal subunit and the early ribosome.

Main Methods:

• Construction of an ancestral proto-tRNA sequence.
• Comparative analysis of sequence and structural identity between the reconstructed proto-tRNA and the 3' upper domain of 16S ribosomal RNA.

Main Results:

• The reconstructed ancestral proto-tRNA sequence exhibited significant sequence identity (51.69%) and structural identity (0.941) with the 3' upper domain of 16S ribosomal RNA.
• A hypothesis is proposed where proto-tRNA fusion led to the emergence of the small ribosomal subunit, acting as an RNA-binding platform.

Conclusions:

• Ancestral tRNAs are plausible precursors to 16S ribosomal RNA.
• The early ribosome may have formed through proto-tRNA fusion and subsequent subunit association mediated by tRNA interactions during primordial genetic code development.