Molecular cloning of the gene encoding the valyl-tRNA synthetase from Bacillus stearothermophilus

The valS gene from the thermophile Bacillus stearothermophilus encoding the valyl-tRNA synthetase has been cloned on a 13.8-kb plasmid. The gene product and its kinetic properties are comparable with those of the native enzyme.     

Response of a phage modification factor to enhanced production of its target molecule.

Escherichia coli cells with plasmids bearing the valS gene were constructed from the Clark-Carbon collection. Their increased valyl-tRNA synthetase (EC 6.1.1.9) activity was not matched by commensurate production of a modifying peptide during T4 infection. Thus, phage vs gene expression is set to modify the normal amount of valyl-tRNA synthetase activity.     

Regulation of the biosynthesis of aminoacyl-transfer ribonucleic acid synthetases and of transfer ribonucleic acid in Escherichia coli. V. Mutants with increased levels of valyl-transfer ribonucleic acid synthetase.

Spontaneous revertants of a temperature-sensitive Escherichia coli strain harboring a thermolabile valyl-transfer ribonucleic acid (tRNA) synthetase were selected for growth at 40 degrees C. Of these, a large number still contain the thermolabile valyl-tRNA synthetase. Three of these revertants contained an increased level of the thermolabile enzyme. The genetic locus, valX, responsible for the enzyme overproduction, is adjacent to the structural gene, valS, of valyl-tRNA synthetase. Determination (by radioimmunoassay) of the turnover rates of valyl-tRNA synthetase showed that the increased level of valyl-tRNA synthetase is due to new enzyme synthesis rather than decreased rates of protein degradation.