Comparison of tryptophan biosynthetic operon regulation in different Gram-positive bacterial species

The tryptophan biosynthetic operon has been widely used as a model system for studying transcription regulation. In Bacillus subtilis, the trp operon is primarily regulated by a tryptophan-activated RNA-binding protein, TRAP. Here we show that in many other Gram-positive species the trp operon is regulated differently, by tRNATrp sensing by the RNA-based T-box mechanism, with T-boxes arranged in tandem. Our analyses reveal an apparent relationship between trp operon organization and the specific regulatory mechanism(s) used.