Contrast the role of the repressor in an inducible system and in a repressible system.

Key Concepts

Inducible Systems

Inducible systems are regulatory mechanisms in which a repressor protein inhibits gene expression until an inducer molecule binds to the repressor. This binding causes a conformational change, allowing the transcription of the gene to proceed. A classic example is the lac operon in E. coli, where the presence of lactose induces the expression of genes necessary for its metabolism.

Repressible Systems

Repressible systems function oppositely to inducible systems, where the repressor is inactive until a corepressor molecule binds to it. This binding activates the repressor, which then attaches to the operator region of the gene, blocking transcription. An example is the trp operon, which is repressed in the presence of tryptophan, preventing the synthesis of enzymes involved in its production.

Repressor Proteins

Repressor proteins are crucial components of gene regulation, acting to inhibit transcription by binding to specific DNA sequences. In inducible systems, they prevent gene expression until an inducer is present, while in repressible systems, they require a corepressor to become active. Understanding the function of these proteins is essential for grasping how cells control gene expression in response to environmental changes.