The trp operon
- The trp operon, found in E. coli bacteria, is a group of genes that encode biosynthetic enzymes for the amino acid tryptophan.
- The trp operon is expressed (turned "on") when tryptophan levels are low and repressed (turned "off") when they are hight.
- The trp operon is regulated by the trp repressor. When bound to tryptophan, the trp repressor blocks expression of the operon.
- Tryptophan biosynthesis is also regulated by attenuation (a mechanism based on coupling of transcription and translation).