If Tryptophan is low in the diet, the repressor changes shape and allows the RNA polymerase to attach and copy the DNA so that Tryptophan can be produced by the cell.
When tryptophan is absent, the repressor protein is in an inactive state, allowing transcription of the trp operon to continue. This is because the repressor protein needs tryptophan to bind to it, enabling it to attach to the operator region and block transcription of the operon.
The trp operon is switched off when tryptophan levels are sufficient in the cell. When tryptophan is abundant, it binds to the trp repressor protein, activating it. This active repressor then binds to the operator region of the trp operon, blocking RNA polymerase from transcribing the genes necessary for tryptophan synthesis. Consequently, the production of enzymes involved in tryptophan biosynthesis is halted.
binding to the trp repressor, causing a conformational change that allows it to bind to the operator region of the trp operon. This blocks RNA polymerase from transcribing the genes, turning off expression of the trp operon.
In E. coli, tryptophan binds to the Trp repressor protein. This binding activates the repressor, allowing it to attach to the operator region of the trp operon, thereby inhibiting the transcription of genes involved in tryptophan biosynthesis. This regulation helps the bacteria maintain homeostasis by preventing the production of tryptophan when levels are sufficient.
The addition of a lactose molecule to the Lac repressor protein is an example of post-translational control in lac operon regulation. This modification prevents the Lac repressor from binding to the operator region, allowing for the transcription of the genes involved in lactose metabolism.
When tryptophan is absent, the repressor protein is in an inactive state, allowing transcription of the trp operon to continue. This is because the repressor protein needs tryptophan to bind to it, enabling it to attach to the operator region and block transcription of the operon.
The trp operon is switched off when tryptophan levels are sufficient in the cell. When tryptophan is abundant, it binds to the trp repressor protein, activating it. This active repressor then binds to the operator region of the trp operon, blocking RNA polymerase from transcribing the genes necessary for tryptophan synthesis. Consequently, the production of enzymes involved in tryptophan biosynthesis is halted.
The tryptophan operon is turned off in the presence of tryptophan because tryptophan acts as a corepressor. When tryptophan levels are high, it binds to the trp repressor protein. This trp-repressor complex then binds to the operator region of the operon, preventing RNA polymerase from transcribing the genes involved in tryptophan synthesis.
binding to the trp repressor, causing a conformational change that allows it to bind to the operator region of the trp operon. This blocks RNA polymerase from transcribing the genes, turning off expression of the trp operon.
In E. coli, tryptophan binds to the Trp repressor protein. This binding activates the repressor, allowing it to attach to the operator region of the trp operon, thereby inhibiting the transcription of genes involved in tryptophan biosynthesis. This regulation helps the bacteria maintain homeostasis by preventing the production of tryptophan when levels are sufficient.
a repressor protein
The addition of a lactose molecule to the Lac repressor protein is an example of post-translational control in lac operon regulation. This modification prevents the Lac repressor from binding to the operator region, allowing for the transcription of the genes involved in lactose metabolism.
The determining factor for the transcription of structural genes of the trp operon is the availability of tryptophan. When tryptophan levels are low, the operon is activated, allowing RNA polymerase to transcribe the genes necessary for tryptophan synthesis. Conversely, when tryptophan is abundant, it binds to the trp repressor protein, enabling it to bind to the operator region and inhibit transcription, effectively preventing unnecessary production of tryptophan.
When the repressor protein in not functioning then the gene that that protein was blocking will be "turned on". BTW its not right to cheat, even on study guides ;)
The regulator
When the cell is not in the presence of tryptophan, it activates a regulatory protein called the trp repressor. This repressor binds to the DNA in the promoter region of the operon controlling tryptophan synthesis, preventing RNA polymerase from transcribing the genes. As a result, the production of enzymes involved in tryptophan synthesis is inhibited.
The operon segment composed of the gene that codes for a protein repressor is called the regulatory gene. This gene produces the repressor protein that can bind to the operator region of the operon, preventing transcription of the structural genes when the repressor is bound.