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General structure/function properties of microbial methionyl-tRNA synthetases
E Schmitt1, M Panvert, Y Mechulam
1Laboratoire de Biochimie, Unité de Recherche Associeé n 1970 du Centre National de la Recherche Scientifique, Ecole Polytechnique, Palaiseau, France.
European Journal of Biochemistry
|June 1, 1997
Summary
Conserved residues in methionyl-tRNA synthetases from Bacillus stearothermophilus and Escherichia coli reveal common structural scaffolds. Site-directed mutagenesis identified key binding sites, confirming similar enzyme folding despite low sequence identity.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Methionyl-tRNA synthetases (MetRS) are crucial enzymes in protein synthesis.
- Sequence analysis of microbial MetRS reveals low overall identity but conserved functional sites.
- The Bacillus stearothermophilus enzyme serves as a model due to its stable, monomeric form.
Purpose of the Study:
- To investigate the functional roles of conserved residues in Bacillus stearothermophilus methionyl-tRNA synthetase.
- To identify specific binding sites for ATP, methionine, tRNA, and zinc ions.
- To compare the structural and functional conservation between B. stearothermophilus and Escherichia coli MetRS.
Main Methods:
- Site-directed mutagenesis of Bacillus stearothermophilus methionyl-tRNA synthetase.
- Biochemical characterization of mutant enzymes.
- Sequence alignment and comparative analysis with Escherichia coli methionyl-tRNA synthetase.
Main Results:
- Mutagenesis confirmed conserved residues are essential for enzyme activity.
- Identified specific residues involved in ATP, methionine, and tRNA binding.
- Localized the zinc ion binding site crucial for enzyme stability and function.
- Demonstrated that B. stearothermophilus MetRS shares a similar three-dimensional fold with E. coli MetRS.
Conclusions:
- Despite low sequence identity (27%), B. stearothermophilus and E. coli MetRS share a conserved structural scaffold.
- Functionally important residues are maintained at similar positions, enabling conserved enzymatic activity.
- The findings suggest a generalizable model for conserved structure-function relationships across various methionyl-tRNA synthetases.