What is the AraC protein?

What is the AraC protein?

• A. Structural protein of the cell wall
• B. A transcriptional regulator that responds to arabinose to modulate PBAD
• C. A metabolic enzyme in glycolysis
• D. A membrane channel protein

Answer: (B)

The main idea here is understanding what AraC does in gene regulation. AraC is a transcriptional regulator that senses arabinose and modulates transcription from the arabinose promoter, PBAD. When arabinose is absent, AraC binds to two operator sites in a way that loops the DNA and represses PBAD, keeping the araBAD genes off. When arabinose is present, AraC changes shape and promotes RNA polymerase binding to PBAD, turning on transcription of araBAD and other genes needed to metabolize arabinose. This dual behavior—repressing without arabinose and activating with arabinose—defines AraC’s role. It’s not a structural protein of the cell wall, a glycolysis enzyme, or a membrane channel, which is why the other options don’t fit. In practice, the arabinose promoter PBAD is a common inducible system in biotechnology, with AraC as the regulator that responds to arabinose to control gene expression.

The main idea here is understanding what AraC does in gene regulation. AraC is a transcriptional regulator that senses arabinose and modulates transcription from the arabinose promoter, PBAD. When arabinose is absent, AraC binds to two operator sites in a way that loops the DNA and represses PBAD, keeping the araBAD genes off. When arabinose is present, AraC changes shape and promotes RNA polymerase binding to PBAD, turning on transcription of araBAD and other genes needed to metabolize arabinose. This dual behavior—repressing without arabinose and activating with arabinose—defines AraC’s role. It’s not a structural protein of the cell wall, a glycolysis enzyme, or a membrane channel, which is why the other options don’t fit. In practice, the arabinose promoter PBAD is a common inducible system in biotechnology, with AraC as the regulator that responds to arabinose to control gene expression.