A more complex isoleucine aptamer with a cognate triplet

Area of Science:

• Biochemistry
• Molecular Biology
• Origin of Life Studies

Background:

• Previous research identified a simple UAUU RNA motif for isoleucine binding.
• This motif was characterized as a small, asymmetric internal loop with conserved isoleucine codon and anticodon triplets.

Purpose of the Study:

• To select and characterize a more complex RNA molecule capable of binding isoleucine.
• To investigate the structural and informational requirements for isoleucine recognition by RNA.

Main Methods:

• Affinity selection using modified primer sequences.
• Information theory analysis to quantify sequence complexity and identify functional regions.

Main Results:

• A new isoleucine-binding RNA was selected, exhibiting a more complex structure (20-nucleotide hairpin loop) than previously identified motifs.
• This new RNA requires significantly more information (4.7 bits) to describe, indicating increased complexity.
• An information profile revealed five short functional loop regions within the new RNA structure.
• A conserved isoleucine anticodon was identified within the new RNA, reinforcing the escaped triplet theory.

Conclusions:

• RNA molecules can evolve complex structures for specific amino acid binding beyond simple motifs.
• The conserved anticodon supports the escaped triplet theory, suggesting RNA-amino acid binding sites as a precursor to the genetic code.
• These findings contribute to understanding the stereochemical basis of the genetic code and the role of RNA in early life.