A Tyrosine-Dependent Riboswitch Controls the Expression of a Tyrosyl-tRNA Synthetase from Acidithiobacillus ferrooxidans
نویسندگان
چکیده
Expression of aminoacyl-tRNA synthetases is regulated by a variety of mechanisms at the level of transcription or translation. A T-box dependent transcription termination / antitermination riboswitch system that responds to charged / uncharged tRNA regulates expression of aminoacyl tRNA synthetase genes in Gram-positive bacteria. TyrZ, the gene encoding tyrosyl-tRNA synthetase from Acidithiobacillus ferrooxidans, a Gram-negative acidophilic bacterium that participates in bioleaching of minerals, resembles the gene from Bacillus subtilis including the 5 ́-untranslated region encoding the riboswitch. Transcription of A. ferrooxidans tyrZ is induced by the presence of tyrosine by a mechanism involving antitermination of transcription. This mechanism is probably adapted to the low supply of amino acids of acidic environments of autotrophic bioleaching microorganisms.
منابع مشابه
Tyrosyl-tRNA synthetase from Escherichia coli. Stoichiometry of ligand binding and half-of-the-sites reactivity in aminoacylation.
The tyrosyl-tRNA synthetase from Escherichia coli binds only 1 mol of tRNA, tyrosine, and tyrosyl adenylate per mol of enzyme dimer. However, like the enzyme from Bacillus stearothermophilus, once one active site is occupied by tyrosyl adenylate the other becomes accessible to bind a further molecule each of tyrosine and ATP. Both bacterial enzymes show biphasic kinetics with respect to tyrosin...
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