Primary structure of yeast mitochondrial DNA-coded phenylalanine-tRNA

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Mitochondria possess their own genetic material, including transfer RNAs (tRNAs).
• The structure and function of mitochondrial tRNAs can differ from their cytoplasmic counterparts.
• Understanding mitochondrial tRNA structure is crucial for comprehending mitochondrial gene expression and evolution.

Purpose of the Study:

• To determine the primary and secondary structure of mitochondrial phenylalanyl-tRNA (tRNAPhe) from Saccharomyces cerevisiae.
• To investigate the potential for aminoacylation by the cytoplasmic phenylalanyl-tRNA synthetase.
• To compare the mitochondrial tRNAPhe structure with known cytoplasmic tRNAs for evolutionary insights.

Main Methods:

• Isolation of mitochondrial tRNAPhe using two-dimensional gel electrophoresis.
• Sequencing via fingerprinting of uniformly labeled 32P-tRNA.
• 5'-end postlabeling techniques for sequence determination.

Main Results:

• The complete nucleotide sequence of Saccharomyces cerevisiae mitochondrial tRNAPhe was elucidated.
• A proposed secondary structure features a bulge in the phiC stem, excluding U50 from base pairing.
• The mitochondrial tRNAPhe lacks structural elements necessary for recognition by yeast cytoplasmic phenylalanyl-tRNA ligase and cannot be aminoacylated by it.

Conclusions:

• The determined sequence and proposed secondary structure provide a detailed molecular characterization of yeast mitochondrial tRNAPhe.
• The inability of yeast cytoplasmic phenylalanyl-tRNA ligase to aminoacylate this mitochondrial tRNA highlights functional divergence.
• Structural comparison did not yield conclusions regarding the endosymbiotic theory of mitochondria evolution.