A2 Genetic Control of Proteins and Control of Gene Expression Practice Test

CAP activation depends on binding of cAMP to CAP. When glucose is abundant, production of cAMP drops because adenylyl cyclase is inhibited. With little or no cAMP, CAP cannot effectively bind to its target promoter and recruit RNA polymerase, so transcription that requires CAP activation is reduced. This is the reason CAP activation decreases when glucose is plentiful.