The different roles of tryptophan transfer RNA in regulating trp operon expression in E. coli versus B. subtilis

Trends Genet. 2004 Aug;20(8):367-74. doi: 10.1016/j.tig.2004.06.007.


Escherichia coli and Bacillus subtilis use different mechanisms of sensing and responding to tryptophan and uncharged tRNA(Trp) as regulatory signals. In E. coli, tryptophan activates a repressor that binds to the trp promoter- operator, inhibiting transcription initiation. In B. subtilis, tryptophan activates an RNA-binding protein, TRAP, which binds to the trp operon leader RNA, causing transcription termination. In E. coli uncharged tRNA(Trp) accumulation stalls the ribosome attempting translation of tandem Trp codons in the leader-peptide coding region of the operon. This stalling permits the formation of an RNA antiterminator structure, preventing transcription termination. In B. subtilis uncharged tRNA(Trp) accumulation activates transcription and translation of the at operon. AT protein inhibits tryptophan-activated TRAP, thereby preventing TRAP-mediated transcription termination. These differences might reflect the unique organizational features of the respective trp operons and their ancestry.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Bacillus subtilis / genetics*
  • Bacillus subtilis / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism
  • Operon / genetics*
  • Promoter Regions, Genetic / genetics
  • RNA, Transfer / genetics*
  • RNA, Transfer / metabolism
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Ribosomes / genetics
  • Ribosomes / metabolism
  • Terminator Regions, Genetic
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription, Genetic / genetics
  • Tryptophan / genetics
  • Tryptophan / metabolism*


  • Bacterial Proteins
  • MtrB protein, Bacteria
  • RNA-Binding Proteins
  • Transcription Factors
  • Tryptophan
  • RNA, Transfer