What is a repressible operon?
1 Answer
An operon that is regulated by a co-repressor (chemical substance) is called as the repressible operon.
Explanation:
The co-repressor is a non-protein compound, which may come from outside or from metabolism within the cell. The operon is switched off when the co-repressor is present.
Example -- Tryptophan Operon
) Formation of amino acid tryptophan needs action of five enzymes in succession. The formation of tryptophan is on because regulator gene R forms an inactive repressor called aporepressor which does not attach itself to operator site. As operator site is free of repressor, the operon system remains on leading to the synthesis of all five enzymes needed for tryptophan formation.
When tryptophan accumulates, a few molecules (of tryptophan) act as co-repressor and bind to inactive repressor activating it. On activation this attaches to the operator, switching off the operon in turn.
