L41 BIOL 4810 Lecture Notes - Lecture 25: Camp Receptor Protein, Regulon, Lac Repressor
2 Nov 2016
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Ex: cap regulation, ~100 genes of carbohydrate metabolism. Regulon: all genes regulated positively (enhanced transcription) and/or negatively (reduced transcription) by a specific regulator protein. Stimulon: all genes responding to a specific external signal (stimulus) by increased or decreased transcription. A stimulon can be characterized by comparing bacterial transcriptome in the presence and absence of the specific stimulus. Crp site is the binding site for camp receptor protein (regulatory factor). Promoter also includes binding sites for rnap and lac repressor. Synthesis of repressor initiates at its own promoter (i promoter). Additional repressor-binding sites exist, 82 nucleotides upstream and 432 nucleotides downstream, respectively, from the transcriptional start point. Binding of the repressor to the operator inhibits transcription of the structural genes. The inducer binds to the repressor, decreasing the affinity of the repressor for the operator. Dissociation of the inactive repressor-inducer complex from the operator permits transcription of the structural genes. Transcription and translation of lac structural genes occurs.
