needed to transcribe the operon. The operon is constitutively transcribed. If tryptophan is present in the environment, the bacterium will inactivate the operon and utilize the free tryptophan. The trp repressor is incapable of binding to the trp operator itself. But when there is free trptophan around, the tryptophan acts as a co-repressor. It binds to the trp repressor and forms a repressor complex. This complex binds to the operator and shuts down transcription.If tryptophan levels decline, the repressor is less likely to be found to a tryptophan molecule. The operator is freed and transcription continues again.Bacteria have complex methods to regulator the expression of certain genes. The operon shows that even though bacteria may seem like simple organism, they have evolved complex systems that have allowed them to survive for billions of years. ...
