The trp Operon - . Tryptophan is therefore a corepressor ....

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The trp Operon Repressible operons are the opposite of inducible operons. Transcription occurs continuously and the repressor protein must be activated to stop transcription. Tryptophan is an amino acid needed by E. coli and the genes that code for proteins that produce tryptophan are continuously transcribed as shown below. If tryptophan is present in the environment, however, E. coli does not need to synthesize it and the tryptophan-synthesizing genes should be turned off. This occurs when tryptophan binds with the repressor protein, activating it. Unlike the repressor discussed with the lac operon, this repressor will not bind to the DNA unless it is activated by binding with tryptophan.
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Unformatted text preview: . Tryptophan is therefore a corepressor . The trp operon is an example of a repressible operon because the structural genes are active and are inactivated when tryptophan is present. Structural Genes Repressor Inducible Operons Inactive Active (inhibits) Repressible Operons Active Inactive (inhibits when activated) Negative Feedback Inhibition In addition to genetic regulation, tryptophan can inhibit the first enzyme in the synthesis pathway. This is an example of feedback inhibition. The presence of high levels of tryptophan inhibits the activity of the enzyme as shown in the biosynthesis pathway below....
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This note was uploaded on 12/15/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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The trp Operon - . Tryptophan is therefore a corepressor ....

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