Describe the role of attenuation in the regulation of tryptophan biosynthesis.

Name: Problem 12, Chapter 15: Essentials of Genetics
Uploaded: 2020-06-29T23:01:58-08:00
Duration: 3 min 5 s
Channel: Dennis Howard
Description: Describe the role of attenuation in the regulation of tryptophan biosynthesis.

step 1 This question asks, what is attenuation? What are the mechanisms by which the attenuator forms w

Describe the role of attenuation in the regulation of...

Key Concepts

Attenuation

Attenuation is a transcriptional regulatory mechanism in bacteria that involves the formation of alternative mRNA secondary structures in a leader region. This mechanism determines whether transcription of a downstream operon will continue or prematurely terminate, thus providing a fine-tuned response to the cellular concentration of a specific amino acid.

Coupled Transcription-Translation

In prokaryotic cells, the processes of transcription and translation occur simultaneously. This coupling allows the ribosome to influence the folding of the nascent mRNA, particularly in leader sequences, thereby playing a critical role in the regulation of gene expression via attenuation.

Leader Peptide and Ribosome Stalling

The leader region of the mRNA includes a short open reading frame that encodes a leader peptide, which is rich in codons for the regulated amino acid. When the amino acid is scarce, ribosomes stall during translation of the leader peptide, causing the mRNA to adopt a structure that prevents the formation of a transcription terminator, thereby allowing full transcription of the operon.

Regulation of Tryptophan Biosynthesis

In the case of tryptophan biosynthesis, the trp operon is controlled by an attenuation mechanism. High levels of tryptophan lead to rapid translation of the leader peptide and the formation of a terminator hairpin in the mRNA, resulting in transcription termination. Conversely, low levels of tryptophan cause ribosome stalling, promoting the formation of an anti-terminator structure that allows the RNA polymerase to transcribe the complete operon.

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