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Primary structure of the Saccharomyces cerevisiae gene for methionyl-tRNA synthetase
Abstract:
The sequence of a 5-kilobase DNA insert containing the structural gene for yeast cytoplasmic methionyl-tRNA synthetase has been determined and a unique open reading frame of 2,253 nucleotides encoding a polypeptide chain of 751 amino acids (Mr, 85,500) has been characterized. The data obtained on the purified enzyme (subunit size, amino acid composition, and COOH-terminal sequence) are consistent with the gene structure. The protein sequence deduced from the nucleotide sequence reveals no obvious internal repeats. This protein sequence shows a high degree of homology with that of Escherichia coli methionyl-tRNA synthetase within a region that forms the putative methionyl adenylate binding site. This strongly suggests that both proteins derive from a common ancestor.
Insights
The gene for yeast cytoplasmic methionyl-tRNA synthetase was sequenced, revealing its structure and relation to bacterial enzymes. This finding suggests a shared evolutionary origin for these essential proteins.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Methionyl-tRNA synthetase is crucial for protein synthesis in all organisms.
- Understanding the structure and evolution of this enzyme provides insights into fundamental biological processes.
Purpose of the Study:
- To determine the DNA sequence of the yeast cytoplasmic methionyl-tRNA synthetase gene.
- To characterize the encoded protein and compare its structure to homologous enzymes.
Main Methods:
- DNA sequencing of a 5-kilobase insert.
- Bioinformatic analysis to identify open reading frames and deduce protein sequence.
- Comparison of yeast and E. coli methionyl-tRNA synthetase sequences.
Main Results:
- A 2,253-nucleotide open reading frame encoding a 751-amino acid protein (Mr, 85,500) was identified.
- Enzyme data (subunit size, amino acid composition) align with the gene sequence.
- High homology was found with E. coli methionyl-tRNA synthetase, particularly in the adenylate binding site.
Conclusions:
- The yeast cytoplasmic methionyl-tRNA synthetase gene structure has been elucidated.
- The deduced protein sequence is consistent with experimental enzyme data.
- Significant sequence homology suggests a common evolutionary ancestor for yeast and E. coli methionyl-tRNA synthetases.