Regulation of tryptophan biosynthesis: Trp-ing the TRAP or how Bacillus subtilis reinvented the wheel.
The Bacillus subtilis tryptophan biosynthetic genes are regulated by TRAP. Radiographic crystallography indicates that the TRAP complex contains 11 identical subunits arranged in a doughnut-like structure termed the beta-wheel. The trpEDCFBA operon is regulated by an attenuation mechanism in which tryptophan-activated TRAP binds to 11 (G/U)AG repeats in the trp leader transcript. TRAP binding blocks formation of an anti-terminator structure, thereby promoting the formation of an overlapping terminator, resulting in transcription termination preceding the structural genes. When TRAP is not activated, it is unable to bind to the transcript, which allows anti-terminator formation and, hence, transcription of the operon. TRAP is also responsible for regulating translation of trpEand trpG. TRAP binding to trp operon readthrough transcripts promotes refolding of the RNA such that the trpE Shine-Dalgarno sequence is sequestered in a hairpin, thus inhibiting TrpE synthesis. In the case of trpG, TRAP binds to nine repeats that overlap the ribosome-binding site, thereby blocking translation.
Babitzke
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Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park 16802, USA. pxb28@psu.edu
D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D015964:Gene Expression Regulation, Bacterial; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics; D014176:Protein Biosynthesis; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D013728:Terminator Regions, Genetic; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D014364:Tryptophan / Q000096:biosynthesis* / Q000378:metabolism
D001426:Bacterial Proteins; C079092:MtrB protein, Bacteria; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D014364:Tryptophan