Trp operon

Definition

The trp operon is a group of genes in bacteria responsible for the synthesis of the amino acid tryptophan. It is a classic example of a repressible operon, where gene expression is inhibited by the end product, tryptophan.

5 Must Know Facts For Your Next Test

1. The trp operon consists of five structural genes: trpE, trpD, trpC, trpB, and trpA.
2. When tryptophan levels are high, tryptophan binds to the repressor protein and activates it to block transcription.
3. In the absence of tryptophan, the repressor protein remains inactive and does not bind to the operator, allowing transcription to proceed.
4. The leader sequence (trpL) contains attenuator regions that help regulate transcription through a mechanism called attenuation.
5. Attenuation involves the formation of stem-loop structures in mRNA that can terminate transcription prematurely based on tryptophan availability.

Review Questions

• What role does tryptophan play in regulating the trp operon?
• How do high levels of tryptophan affect the repressor protein in the trp operon?
• What is attenuation and how does it contribute to gene regulation in the trp operon?

Related terms

Lac Operon:

A set of genes involved in lactose metabolism that is regulated by both an inducer (lactose) and a repressor.

Repressible Operon: An operon that is usually active but can be inhibited when a specific molecule binds to a regulatory protein.

Attenuation: A regulatory mechanism where translation influences transcription termination based on metabolite availability.