Operator gene

Operator Gene

The operator gene is a crucial component of the operon model of prokaryotic gene expression. It is a segment of DNA to which a transcription factor (a repressor protein) can bind, thereby controlling the expression of genes located downstream.

Function

The operator gene functions as an on-off switch for the control of gene expression. It is located between the promoter gene and the structural genes in the operon. When a repressor protein binds to the operator gene, it prevents the progression of RNA polymerase along the DNA strand, thus inhibiting the transcription of the downstream genes.

Lac Operon

A classic example of an operator gene is found in the lac operon of Escherichia coli. In the absence of lactose, the lac repressor binds to the operator gene, preventing the transcription of the genes responsible for lactose metabolism. When lactose is present, it binds to the repressor, causing a conformational change that prevents the repressor from binding to the operator. This allows the genes to be transcribed and the enzymes necessary for lactose metabolism to be produced.

Trp Operon

Another example is the trp operon, which controls the production of tryptophan in E. coli. When tryptophan levels are high, it acts as a co-repressor, binding to the trp repressor and enabling it to bind to the operator gene. This prevents the transcription of the genes responsible for tryptophan synthesis.

See Also

• Operon
• Gene expression
• Transcription factor
• Lac operon
• Trp operon