TrpD

Definition

trpD is a gene that encodes the enzyme anthranilate phosphoribosyltransferase, which is involved in the tryptophan biosynthesis pathway. This gene plays a crucial role in the regulation of gene expression through the operon theory, specifically in the tryptophan operon.

5 Must Know Facts For Your Next Test

1. The trpD gene is part of the tryptophan operon, a genetic regulatory system that controls the expression of genes involved in tryptophan biosynthesis.
2. Anthranilate phosphoribosyltransferase, the enzyme encoded by the trpD gene, catalyzes a crucial step in the tryptophan biosynthesis pathway.
3. Regulation of the tryptophan operon, including the trpD gene, is controlled by the availability of tryptophan in the cell, which acts as a corepressor to the trp repressor protein.
4. When tryptophan is abundant, the trp repressor binds to the operator region of the tryptophan operon, preventing the transcription of the trpD and other tryptophan biosynthesis genes.
5. In the absence of tryptophan, the trp repressor dissociates from the operator, allowing the expression of the trpD gene and the production of anthranilate phosphoribosyltransferase to continue tryptophan synthesis.

Review Questions

• Explain the role of the trpD gene in the tryptophan biosynthesis pathway.
  • The trpD gene encodes the enzyme anthranilate phosphoribosyltransferase, which catalyzes a key step in the tryptophan biosynthesis pathway. This enzyme converts anthranilate and 5-phosphoribosyl-1-pyrophosphate (PRPP) into N-(5'-phosphoribosyl)anthranilate, an important intermediate in the production of tryptophan. The trpD gene is part of the tryptophan operon, a genetic regulatory system that controls the expression of genes involved in tryptophan synthesis in response to the availability of tryptophan in the cell.
• Describe how the regulation of the trpD gene is influenced by the tryptophan operon.
  • The expression of the trpD gene is regulated by the tryptophan operon, a genetic regulatory system that controls the biosynthesis of tryptophan. When tryptophan is abundant in the cell, it acts as a corepressor, binding to the trp repressor protein and causing it to bind to the operator region of the tryptophan operon, including the trpD gene. This binding prevents the transcription of the trpD gene and the other tryptophan biosynthesis genes, reducing the production of tryptophan. Conversely, when tryptophan is scarce, the trp repressor dissociates from the operator, allowing the expression of the trpD gene and the continued synthesis of tryptophan.
• Analyze the significance of the trpD gene in the context of the operon theory and its implications for understanding gene regulation in bacteria.
  • The trpD gene is a crucial component of the tryptophan operon, which serves as a model system for understanding gene regulation in bacteria through the operon theory. The regulation of the trpD gene, encoding the enzyme anthranilate phosphoribosyltransferase, demonstrates how the availability of a specific metabolite (in this case, tryptophan) can directly influence the expression of genes involved in its biosynthesis. This feedback mechanism, where the end product of a metabolic pathway acts as a corepressor to its own synthesis, is a fundamental principle of operon theory and gene regulation. The study of the trpD gene and its role in the tryptophan operon provides valuable insights into how bacteria efficiently coordinate the expression of genes to maintain homeostasis and respond to changing environmental conditions.

Related terms

Tryptophan Operon: A genetic regulatory system in bacteria that controls the expression of genes involved in the biosynthesis of the amino acid tryptophan.

Anthranilate Phosphoribosyltransferase: An enzyme encoded by the trpD gene that catalyzes a key step in the tryptophan biosynthesis pathway, converting anthranilate and 5-phosphoribosyl-1-pyrophosphate (PRPP) into N-(5'-phosphoribosyl)anthranilate.

Tryptophan Biosynthesis:

The metabolic pathway in which the essential amino acid tryptophan is synthesized from simpler precursor molecules, involving a series of enzymatic reactions.