Question

The enzymes required for protein synthesis of the amino acid tryptophan in E. coli are all encoded in a single transcription unit, the trp operon. Transcription of the trp operon is only ignited when the cell has low levels of free tryptophan. Briefly describe how initiation of transcription of the trp operon is regulated in response to the availability of free tryptophan.

Answer 1

In the absence or low level of tryptophan , the operator region of the operon is open as the tryptophan regulatory repressor molecule is inactive , thus free the site of operator for polymerase to carry out the function. When the tryptophan concentration increases as it act as corepressor it bind to apprepressor and bind to operator blocking the operon function. Thus the low level of tryptophan active the normal on trp operon.