Question

The trp operon of E. coli controls expression of five enzymes that are involved in the biosynthesis of the amino acid tryptophan. A trp repressor protein (trpR) binds to the trp operator to prevent transcription when tryptophan is present. When would the tryptophan synthesis enzymes be made if the trpR gene was mutated?

Answer 1

Answer:

Tryptophan synthesis enzymes be made during low level of cellular tryptophan.

Explanation:

Tryptophan operon  contain 3 regulatory gene(trpR,trpP and trpO) and 5 structural genes(trpE,trpD,trpC,trpB and trpA) .trpR encodes the repressor protein that interacts with tryptophan present in the media and then the tryptophan repressor complex binds to the operator region to block the transcription of the structural genes of tryptophan operon.

   Here tryptophan acting as a corepresor.During mutation of trpR gene tryptophan biosynthesis enzymes will be synthesized only when the cellular tryptophan level remains very low.