Conservation of a transcription antitermination mechanism in aminoacyl-tRNA synthetase and amino acid biosynthesis genes in gram-positive bacteria.

Most of the aminoacyl-tRNA synthetase genes identified to date in the Gram-positive bacterium Bacillus subtilis have been found to be regulated by readthrough of a transcriptional terminator located in the mRNA leader region, upstream of the start of the coding sequence. All of these leader regions contain a series of conserved structural features, as well as a single codon displayed at a precise position within the structure, which has been shown for tyrS to be responsible for the specificity of the response to limitation for tyrosine. The structural features critical for transcription antitermination in Bacillus aminoacyl-tRNA synthetase genes were found in the B. subtilis ilv-leu biosynthetic operon, the Lactobacillus casei valS gene, the Corynebacterium glutaminicum argS gene, and three amino acid biosynthesis operons in Lactobacillus casei and Lactococcus lactis, suggesting that all of these genes are likely to be regulated by a similar antitermination mechanism. This regulatory system therefore appears to be widespread in Gram-positive bacteria.