A Double Dose of Trp Regulation

Amino acid synthesis is tightly controlled in bacteria by a system in which the amino acids themselves, as well as their corresponding transfer RNAs (tRNAs), regulate production. For example, in Bacillus subtilis, the mechanism for regulating tryptophan (Trp) synthesis involves an antiterminator protein called TRAP, which is activated by Trp. However, TRAP activity is antagonized by a protein called anti-TRAP (AT), where the synthesis of AT is induced by uncharged tRNATrp. Chen and Yanofsky now show another level of regulation for the Trp operon in which uncharged tRNATrp also regulates the translation of AT through tandem Trp codons in a leader peptide coding sequence. This mechanism is somewhat reminiscent of the classical Trp attenuation system in Escherchia coli; however, the leader peptide in B. subtilis exerts its effect at the level of translation instead of transcription termination, as seen in E. coli. The authors term the B. subtilis system "regulatory sophistication" because it shows both transcriptional and translational regulation of AT in response to tRNATrp. G. Chen, C. Yanofsky, Tandem transcription and translation regulatory sensing of uncharged tryptophan tRNA. Science 301, 211-213 (2003). [Abstract] [Full Text]