Catabolite activator protein (CAP) is described as a positive regulator that responds to falling glucose levels. What molecule binds CAP to activate it, and where does the activated complex then bind?
ATryptophan binds CAP, and the complex binds the trp operator to block RNA polymerase
BLactose binds CAP directly, bypassing any need for cyclic AMP
CGlucose itself binds CAP, and the complex binds ribosomal RNA genes
DCyclic AMP binds CAP, and the complex binds promoters of genes for alternate sugars
Answer & Solution
Correct answer: D. Cyclic AMP binds CAP, and the complex binds promoters of genes for alternate sugars
1. When glucose levels decline in the cell, accumulating cAMP binds to the positive regulator catabolite activator protein, or CAP.
2. When cAMP binds CAP, the complex binds to the promoter region of the genes needed to use alternate sugar sources.
3. This increases the ability of RNA polymerase to bind the promoter and transcribe those genes.
4. Tryptophan and the trp operator belong to the separate trp repressor system, not the CAP activator system.
5. Lactose does not bind CAP directly; the lac operon instead requires the cAMP-CAP complex together with the absence of the repressor.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 16 "Gene Expression", section Catabolite Activator Protein (CAP): An Activator Regulator_
Related questions
Regulatory proteins that bind to the untranslated regions of an RNA molecule can change hoSome new cancer drugs are designed around individual patients' gene expression patterns raThe protein c-Flip exists in two forms, a long form and a short form, and is involved in tIn cancer cells, silenced genes commonly show a specific combination of epigenetic changesThe gene myc encodes a transcription factor that becomes an oncogene when aberrantly activOne tumor suppressor gene is described as the most studied of its kind and is mutated in oCyclin B is a protein that normally serves as a cell-cycle checkpoint protein. In cancer cA protein tagged with an ubiquitin group is marked for a specific fate inside the cell. Wh