分子生物学分子生物学 (8).pdf
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1、Chapter 5Regulation of Gene Expression5.2 Mechanism of gene expression regulation in prokaryotes(Regulation of transcription initiation)5.2.1 factor and regulation of transcription initiationcore enzymeholoenzyme It Regulates the binding of RNA polymerase tospecific DNA region;It ensures the stable
2、binding of RNA polymeraseto a specific promoter region.(1)factorDifferent factors determine the specificrecognition and binding of RNA polymerase toone or one set of promoter sequences.The first discovered factor:70Newly discovered factors:32、54、28(2)Promoter sequencesTranscription start points-35 s
3、equences-10sequencesTTGACATTAACTTTTACATATGATTTTACATATGTTTTGATATATAATCTGACGTACTGTN17N16N17N16N16N7N7N6N7N6AAAAAtrptRNATyrlacrecAAra BADTTGACATATAATConsensus sequencesThe common sequences determinetranscriptionalactivity of promoter.Some specific factors(proteins)ensure the specificrecognition and bin
4、ding ability of RNA polymeraseto one or a set of promoter sequences.5.2.2 Negative regulation of transcription initiation in prokaryotes.Lactose operon(lac)is the classic model ofnegative regulation of gene transcription inprokaryotes.Structure of lactose operon Structural genesZ:beta galactosidase
5、Y:lactose permeaseA:galactoside trans-acetylaseRegulatory sitesCAP binding sitePromoterOperatorZYAOPDNARepressor proteinmRNARepressor protein IDNAZYAOPWith glucose,no lactoseNegative regulation of repressor proteins Repressor genemRNARepressor protein IDNAZYAOPpolWith glucose,no lactoseNegative regu
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