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Microbiology. 1998 Aug;144 ( Pt 8):2103-11.

Transcription of the trp operon in Lactococcus lactis is controlled by antitermination in the leader region.

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Laboratoire de Génétique Microbienne, Institut National de la Recherche Agronomique, Jouyen-Josas, France.


The regulatory functions of the leader region preceding the Lactococcus lactis trp operon have been studied by mutagenesis analysis. This leader presents striking similarity to 'T-box' leaders found upstream of many Gram-positive aminoacyl-tRNA synthetase genes and some amino acid biosynthesis operons, which are controlled by antitermination through interaction of the leader transcript with cognate uncharged tRNA. A region of the L. lactis leader transcript also contains a series of (G/U) AG repeats which, in Bacillus, are involved in the binding of the trp RNA-binding protein (TRAP) which controls trp transcription. A screen was developed for the isolation of regulatory mutants affected in the leader region. All spontaneous mutants contained deletions; point mutations were only obtained after UV-induced mutagenesis. All mutations affected the putative transcription terminator upstream of the trp operon, demonstrating that trp is indeed controlled by transcription antitermination.

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