Variation of the acceptor-anticodon interstem angles among mitochondrial and non-mitochondrial tRNAs

Area of Science:

• Molecular Biology
• Structural Biology
• Biophysics

Background:

• The canonical cloverleaf secondary and L-shaped tertiary structures are considered universal for transfer RNAs (tRNAs).
• Metazoan mitochondrial tRNAs frequently deviate from canonical structures, often being truncated by missing specific arms.

Purpose of the Study:

• To investigate the structural diversity of canonical and non-canonical tRNAs, focusing on metazoan mitochondrial variants.
• To determine if truncated tRNAs maintain the universal L-shaped tertiary conformation.

Main Methods:

• Analysis of 11 tRNA species (mitochondrial, non-mitochondrial, canonical, non-canonical) in solution.
• Utilized transient electric birefringence to measure apparent interstem angles.
• Extended tRNA transcripts with duplex RNA helix to facilitate measurements.

Main Results:

• Observed greater global structural variation among tRNAs than previously suggested by crystallographic data.
• Truncated metazoan mitochondrial tRNAs exhibit more obtuse acceptor-anticodon interstem angles compared to canonical tRNAs.
• The magnesium dependence of the interstem angle differs between truncated and canonical tRNA species.

Conclusions:

• The canonical L-shaped tertiary structure is not universally conserved across all tRNA types, especially in truncated metazoan mitochondrial tRNAs.
• Truncated tRNAs possess distinct structural constraints and conformations, indicating a broader spectrum of tRNA structural possibilities.