MCAT® ExamBiological and Biochemical Foundations of Living SystemsMedium
A research team is investigating a novel protein that acts as a transcription factor. They discover that the protein's affinity for DNA significantly increases when a specific sugar molecule binds to a site distant from the DNA-binding domain. This binding event induces a conformational change in the protein, allowing it to more effectively regulate gene expression. What type of regulation is being described?
- AAllosteric regulation
- BCovalent modification
- CFeedback inhibition
- DCompetitive inhibition
Show answer & explanationAnswer & explanation
Correct answer: A. Allosteric regulation
Allosteric regulation involves a molecule binding to a site on an enzyme or protein (the allosteric site) that is distinct from the active site or DNA-binding domain, causing a conformational change that alters the protein's activity. In this scenario, the sugar molecule binds to a distant site, leading to increased DNA affinity.
Why the other options are wrong
- B. Covalent modification involves the addition or removal of a chemical group (e.g., phosphorylation) to alter protein activity.
- C. Feedback inhibition occurs when the end product of a metabolic pathway inhibits an enzyme earlier in the pathway.
- D. Competitive inhibition involves an inhibitor binding to the active site, competing with the substrate.
Allosteric Regulation
Regulation of an enzyme or protein by binding an effector molecule at a site other than the enzyme's active site, which induces a conformational change that alters the protein's activity.
- Effector binds to an allosteric site, not the active site.
- Causes a conformational change in the protein.
- Can either activate or inhibit protein function.
- Important for regulating metabolic pathways.
Memory trick: All-star regulators change shape from afar.