Structural dynamics of a mitochondrial tRNA possessing weak thermodynamic stability

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• RNA folding dynamics are crucial for diverse RNA functions.
• The conformational states of weakly stable RNAs remain poorly understood.
• Understanding RNA folding pathways informs RNA-based therapeutics and diagnostics.

Purpose of the Study:

• To investigate the folding dynamics of weakly stable human mitochondrial (hmt) leucine tRNA.
• To elucidate the role of post-transcriptional modifications in RNA structural stability and dynamics.
• To explore the functional implications of RNA conformational flexibility.

Main Methods:

• Utilized a precise folding assay to track the formation of native aminoacylable tRNA.
• Compared folding dynamics between unmodified and fully modified hmt leucine tRNA.
• Analyzed the thermodynamic stability and interconvertibility of native and intermediate RNA conformers.

Main Results:

• The folding of hmt leucine tRNA is hierarchical, featuring a distinct kinetic folding intermediate.
• Native and intermediate conformers exhibit minimal stability difference (1.2 kcal/mol) and are readily interconvertible.
• Post-transcriptional modifications result in a more constrained native structure, eliminating intermediate conformational sampling.

Conclusions:

• Weakly stable RNAs may utilize conformational switching for biological function, especially in the absence of chaperones.
• RNA structural dynamics, including access to pretransition state conformers, may be vital for enzyme recognition and modification.
• Reduced conformational sampling in modified tRNAs can enhance translational efficiency.