The tryptophan operon is a repressible operon system found in bacteria, such as Escherichia coli, that regulates the production of the amino acid tryptophan. This operon consists of genes necessary for tryptophan synthesis. When tryptophan levels are low, the operon is active, allowing for the production of tryptophan. Conversely, when tryptophan is abundant, it binds to the repressor protein, activating it. The activated repressor then binds to the operator region of the operon, inhibiting gene expression and halting tryptophan production.