④ Promoter Operator Repressor bound to operator High glucose DNA P O Low cAMP No transcription CAP Low lactose CAP site 2 cAMP Repressor DNA Low glucose No transcription High cAMP Low lactose Polymerase DNA Low level transcription: 3 zy a polymerase does not High glucose bind promoter efficiently Low cAMP Transcription High lactose Maximal level CAMP of transcription: 4 DNA CAP enhances Low glucose polymerase binding High cAMP Transeription High lactose