During high levels of TRP attenuation, what structure is formed?

The process of TRP attenuation is a regulatory mechanism in prokaryotes that controls the expression of the tryptophan operon. When tryptophan levels are high, the formation of a terminator hairpin loop occurs. This structure is crucial for transcription termination.

During high levels of tryptophan, the ribosome translates the leader peptide quickly, allowing the formation of a specific hairpin structure in the mRNA that causes RNA polymerase to disengage from the DNA, stopping transcription prematurely. This terminator hairpin loop effectively signals the cell to halt production of the enzymes needed for tryptophan synthesis, as the cell does not need to produce more tryptophan when it is already abundant.

In contrast, if tryptophan levels are low, an antiterminator hairpin loop can form which prevents termination and allows the transcription of the structural genes necessary for tryptophan synthesis. Other structures like promoter regions and structural genes relate to different aspects of gene regulation and expression but do not specifically pertain to the mechanism of attenuation itself under high tryptophan conditions.