Functions of trp Operon - The first two genes trpE and trpD code for polypeptides that make up the first enzyme in the pathway. The third gene, trpC codes for a single polypeptide enzyme that catalyses the second step.

The last genes trpB and trpA code for the two polypeptides of the enzyme that carry out the third and last step in the pathway.

When tryptophan is present in the media, it binds to the repressor and induces conformational change. Thus the repressor binds to the operator gene.