Repressor

Repressor

A Repressor is a DNA-binding protein that regulates the expression of one or more genes by binding to the operator or associated silencers. A DNA-binding repressor blocks the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes into messenger RNA. Some repressors are allosteric proteins that change their binding affinity to the operator in the presence of a small molecule ligand.

Function

Repressors are common types of transcription factors in prokaryotes. They function by binding to the operator, a specific DNA sequence upstream of the promoter. This binding blocks RNA polymerase from initiating transcription. Repressors can be classified into two types: those that bind to the operator in the absence of a corepressor and those that bind in the presence of an inducer.

Types of Repressors

Aporepressor

An Aporepressor is a repressor that binds to the operator in the absence of a corepressor. This type of repressor is inactive when binding to the operator and requires a corepressor to function.

Holorepressor

A Holorepressor is a repressor that binds to the operator in the presence of an inducer. This type of repressor is active when binding to the operator and does not require a corepressor to function.

See Also

• Operator (genetics)
• Promoter (genetics)
• Transcription factor
• Gene expression

References

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