Influence of Sequence and Covalent Modifications on Yeast tRNA Dynamics

Area of Science:

• Structural Biology
• Molecular Dynamics Simulations
• Biochemistry

Background:

• Modified nucleotides are integral components of transfer RNA (tRNA).
• These covalent modifications are crucial for regulating tRNA function.
• Understanding how modifications influence tRNA dynamics is essential for deciphering their functional roles.

Purpose of the Study:

• To investigate the impact of nucleotide modifications on tRNA dynamics using molecular dynamics (MD) simulations.
• To compare the structural flexibility and correlated motions between modified and unmodified tRNAs.
• To elucidate how modifications affect specific tRNA domains, such as the anticodon stem-loop (ASL).

Main Methods:

• Utilized X-ray crystal structures of tRNA(Asp), tRNA(Phe), and tRNA(iMet) as starting points.
• Performed extensive explicit solvent MD simulations (6 μs total) using the AMBER package.
• Analyzed root-mean-square deviations (RMSD), sugar pucker, water residence times, principal component analysis (PCA), and base stacking.

Main Results:

• Modifications induced significant rigidity in tRNA(Phe) globally, but increased flexibility in the anticodon stem-loop (ASL) of other tRNAs.
• Modified tRNAs exhibited altered correlated motions and distinct water interaction patterns, particularly pseudouridines favoring 3'-endo conformation.
• The study revealed region-specific effects of modifications, increasing rigidity in some areas while enhancing flexibility in others.

Conclusions:

• Covalent modifications on tRNA do not uniformly increase rigidity; their effects are complex and region-dependent.
• Fine-tuning of ASL rigidity and flexibility by modifications is critical for balancing codon recognition and ribosomal translocation.
• MD simulations provide valuable insights into the dynamic consequences of tRNA modifications, impacting their biological roles.