tRNATrpas a key element of antitermination in theLactococcus lactis trpoperon
Open Access
- 1 July 1998
- journal article
- research article
- Published by Wiley in Molecular Microbiology
- Vol. 29 (1), 61-74
- https://doi.org/10.1046/j.1365-2958.1998.00903.x
Abstract
The expression of the trp operon of Lactococcus lactis is regulated in response to tryptophan availability by a mechanism of transcription antitermination. We present evidence in support of a previously described model involving tRNATrp as a key element in the sensing of tryptophan levels and the realization of the regulatory response to tryptophan limitation. In agreement with this model, two sites of presumed direct interaction between the trp leader transcript and tRNATrp are found to be of crucial importance for efficient antitermination. These correspond to the specifier codon, which presumably interacts with the anticodon in the tRNA, and a sequence complementary to, and presumably interacting with, the acceptor stem of the tRNA. Through these interactions, uncharged tRNATrp is believed to stabilize an antiterminator conformation of the trp leader transcript, thus allowing transcription and expression of the structural genes of the operon. For the first time, we present direct evidence that it is the ratio of uncharged to charged tRNA that is important for the regulation of antitermination, rather than the absolute amount of uncharged tRNA. In addition, our results indicate that the codon–anticodon interaction, although contributing largely to the efficiency of the regulatory response, is not strictly indispensable, which suggests the existence of additional interactions between mRNA and tRNA. Finally, we describe a possible additional level of regulation, superimposed and dependent on tRNA‐mediated antitermination control, that is based on the processing of the trp leader transcript. Together with the regulation mechanisms described earlier for the Escherichia coli and Bacillus subtilis trp operons, this constitutes the third different mechanism of transcript elongation control found to be involved in the regulation of an operon of which the structural genes are highly conserved.Keywords
This publication has 33 references indexed in Scilit:
- Aminoacyl‐tRNA synthetase gene regulation in Bacillus subtilis: induction, repression and growth‐rate regulationMolecular Microbiology, 1995
- The structure of trp RNA-binding attenuation proteinNature, 1995
- Regulation of the Bacillus subtilis trp operon by an RNA‐binding proteinMolecular Microbiology, 1994
- Conservation of a Transcription Antitermination Mechanism in Aminoacyl-tRNA Synthetase and Amino Acid Biosynthesis Genes in Gram-positive BacteriaJournal of Molecular Biology, 1994
- tRNA as a positive regulator of transcription antitermination in B. subtilisCell, 1993
- EVOLUTION OF A BIOSYNTHETIC PATHWAY: THE TRYPTOPHAN PARADIGMAnnual Review of Microbiology, 1989
- Construction of a vector plasmid family and its use for molecular cloning in Streptococcus lactisBiochimie, 1988
- Construction of a single-copy integration vector and its use in analysis of regulation of the trp operon of Bacillus subtilisGene, 1986
- New versatile plasmid vectors for expression of hybrid proteins coded by a cloned gene fused to lacA gene sequences encoding an enzymatically active carboxy-terminal portion of β-galactosidaseGene, 1983
- Attenuation in the control of expression of bacterial operonsNature, 1981