[Regulation of lysyl-tRNA synthetase of Escherichia coli K12].

In Escherichia coli K 12, addition of lysine to the growth medium does not lead to a repression of the synthesis of the lysyl-tRNA synthetase. On the contrary, by use of a strain bradytrophic for one of the lysine biosynthetic enzymes, a shift from a medium containing lysine to minimal medium leads to an increase in the specific activity for this enzyme. This increase is discrete (1.5 fold) but reproducible. Thus it may be assumed that lysyl-tRNA synthetase belongs to the lysine regulon.