Unilateral aminoacylation specificity between bovine mitochondria and eubacteria

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Biochemistry

Background:

• Mitochondria are organelles with bacterial origins.
• Aminoacyl-tRNA synthetases (aaRS) are crucial for protein synthesis, attaching amino acids to tRNAs.
• Understanding the evolutionary relationship between mitochondrial and bacterial aaRS is key to deciphering organelle evolution.

Purpose of the Study:

• To investigate the aminoacylation specificity of bovine mitochondrial aaRS towards bacterial tRNAs.
• To compare the tRNA recognition mechanisms between mitochondrial and bacterial aaRS.
• To explore the evolutionary implications of observed differences in aminoacylation specificity.

Main Methods:

• In vitro aminoacylation assays were performed using bovine mitochondrial and bacterial (E. coli, T. thermophilus) aaRS and tRNAs.
• Specificity was assessed by measuring the charging of cognate and non-cognate tRNAs by different synthetases.
• Analysis focused on five specific amino acid-tRNA synthetase systems.

Main Results:

• Bovine mitochondrial synthetases efficiently charged both mitochondrial and bacterial tRNAs.
• Bacterial synthetases showed poor charging of mitochondrial tRNAs.
• Four out of five mitochondrial synthetases (phenylalanyl-, threonyl-, arginyl-, and lysyl-) strictly discriminated cognate from non-cognate bacterial tRNAs.
• Mitochondrial seryl-tRNA synthetase, however, misacylated bacterial tRNAs, indicating less stringent recognition.

Conclusions:

• Mitochondrial aaRS exhibit a degree of conservation with bacterial counterparts, particularly in anticodon recognition by four synthetases.
• The observed unilateral aminoacylation suggests that mitochondrial tRNA recognition mechanisms have simplified compared to bacterial systems.
• This simplification likely reflects the reduced complexity of animal mitochondrial tRNAs and their limited number of species.