Research article
The tyrosyl-tRNA synthetase like gene located in the tyramine biosynthesis cluster of Enterococcus durans is transcriptionally regulated by tyrosine concentration and extracellular pH
Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Carretera de Infiesto s/n, 33300 Villaviciosa, Spain
BMC Microbiology 2012, 12:23 doi:10.1186/1471-2180-12-23
Published: 14 February 2012Abstract
Background
The tyramine producer Enterococcus durans IPLA655 contains all the necessary genes for tyramine biosynthesis, grouped in the TDC cluster. This cluster includes tyrS, an aminoacyl-tRNA synthetase like gene.
Results
This work shows that tyrS was maximally transcribed in absence of tyrosine at acidic pH, showing a greater than 10-fold induction in mRNA levels over levels occurring in presence of tyrosine. Mapping of the tyrS transcriptional start site revealed an unusually long untranslated leader region of 322 bp, which displays the typical features of the T box transcriptional attenuation mechanism. The tyrosine concentration regulation of tyrS was found to be mediated by a transcription antitermination system, whereas the specific induction at acidic pH was regulated at transcription initiation level.
Conclusions
The expression of the tyrS gene present in the TDC cluster of E. durans is transcriptionally regulated by tyrosine concentration and extracelular pH. The regulation is mediated by both an antitermination system and the promoter itself.
