BMS1062 Lecture Notes - Catabolite Repression, Trp Operon, Tryptophan
Document Summary
Rna binds to the promoter (1st step in transcription) Promoter sequences determine where rna polymerase starts transcription (e. g. tata box in eukaryotes) Negative regulation (repressor) a regulatory protein is used to stop transcription of a gene (turns promoter off) Positive regulation (activator) a regulatory protein is required before the gene is efficiently transcribed (turn promoter on) Promoter is off when rna polymerase can"t bind and begin transcription. The place where the repressor binds is called the operator site. Controls the metabolism of lactose to obtain energy. Only want to express the gene when lactose is present. Negative regulation by lactose repressor (lacl) Cap activates transcription after binding camp: cap is an allosteric protein, bent dna allows rna polymerase to access the promoter more efficiently. Cap only activates transcription efficiently in the absence of lac repressor. So: high levels of lac operon expression when: glucose is absent, lactose is present.