分子生物学Chapter-3

Chapter3/第3章,Chapter3TranscriptioninProkaryotes:MechanismandRegulation3.1WhyUseanRNAIntermediate?3.2MechanismofTranscription3.3RegulationofGeneExpressioninProkaryotes3.4Experiments,第3章原核生物转录：机理与调控3.1为什么使用RNA作为中间物？3.2转录机理3.3原核生物基因表达调控3.4实验研究,3.1WhyUseanRNAintermediate?3.1为什么使用RNA作为中间物？,Chromosomesarelargeandcomplex,Lowefficiency!,DNA,Protein,Ribosome,DNAmustbestablee,OnemRNAmanyproteins,Moreopportunitiesforregulation,3.2MechanismofTranscription3.2转录机理,3.2.1Promoters/启动子,10boxand35box,CCAGGCTTTACACTT-CGTATGTTGTGTGGAATTCTTTTTGATGCAATT-ACTATAATAGACAGGGTAGGCGGTGTTGACATA-GTGATACTGAGCACATCA,-35box-10box+1,Consensussequence/共有序列,CCAGGCTTTACACTT-CGTATGTTGTGTGGAATTCTTTTTGATGCAATT-ACTATAATAGACAGGGTAGGCGGTGTTGACATA-GTGATACTGAGCACATCA,-35box-10box+1,TATAAT,TTGACA,Consensussequences,Consensussequence:ageneralizedsequencefromwhichmostactualsequencesdifferverylittleornotatall.（共有序列：一种普遍的序列，大多数实际的序列与它相差很小或完全相同。）,3.2.2RNAPolymerase/RNA聚合酶,Coreenzymevs.Holoenzyme,Holoenzymestartstranscriptionatpromoters,Coreenzymestartstranscriptionatrandom,CatalyticareaofRNApolymerase,3.2.3TranscriptionMechanism3.2.3转录机理,Initiation/起始Elongation/延伸Termination/终止,1.Initiation/起始,Initiation/起始,2.Elongation/延伸,Thepolymerizationreaction聚合反应,RNAsynthesis:53,Proofreading/校正,RemoveU,AddC,NowshowingTranscription,File:biophoto7LifeTranscription.(5),3.Termination/终止,Intrinsictermination内在型终止-dependenttermination依赖型终止,Intrinsictermination/内在型终止,Basepair/碱基对,-dependenttermination/依赖型终止,Rhoproteins,X-RayCrystalStructureOfRhoproteinMMDBID:24381,NowshowingBacterialTranscription,File:biophoto7Genetics:AConceptualApproachBacterialtranscription(6).,3.3Regulationofgeneexpressioninprokaryotes3.3原核生物基因表达调控,3.3.1CoordinateRegulation3.3.2TheLacOperon3.3.3TheTrpOperon3.3.4Ara&GalOperons,3.3.1协同调控3.3.2乳糖操纵子3.3.3色氨酸操纵子3.3.4阿拉伯糖与半乳糖操纵子,Regulationofgeneexpression基因表达调控,ConditionA,Regulationofgeneexpression基因表达调控,ConditionB,3.3.1CoordinateRegulation协同调控,PolycistronicmRNA多顺反子mRNA,PolycistronicmRNA,Translation,Protein1,Protein2,Protein3,3.3.2ThelacOperon/乳糖操纵子,Thelacoperon,1.TheConditionsoflactoseMetabolism1.乳糖代谢的条件,E.coli:“Thisismyfavorite!”,乳糖,半乳糖,葡萄糖,Howtouselactose/如何利用乳糖,E.coli:“Ineedlactosepermease,-galactosidase,andtransacetylase.”,Whentouselactose/何时利用乳糖,E.coli:“Iwilluselactoseonlywhenthereisnoglucoseandthereislactose.”,Glucose+Lactose+,GlucoseLactose,GlucoseLactose+,RegulatedExpressionofLactoseMetabolizingGenes乳糖代谢基因表达调控,1.NegativeRegulationthelacRepressor负调控lac阻遏蛋白2.PositiveRegulationCAP正调控CAP,2.NegativeRegulationthelacRepressor负调控lac阻遏蛋白,NegativeRegulationthelacRepressor负调控lac阻遏蛋白,3.PositiveRegulationCAP正调控CAP,CAP-cAMPcomplex,cAMP,CAP,DNA,CAP,cAMP,AdenylylCyclase(AC),cAMP,ATP,AC,GlucoseinhibitstheactivityofAC.,CAP“Theaccelerator”lacrepressor“Thebrake”,Brake刹车,Accelerator加速器,NowshowingThelacoperon,File:biophoto7Genetics:AConceptualApproachThelacoperon(15),3.3.3TheTrpOperon/色氨酸操纵子,Tryptophan,OH,OH,1.NegativeRegulationHighTrplevel,NegativeRegulationlowTrplevel,lacrepressorvs.trprepressor,PromoterLeader,-,attenuator,trpE,trpD,Aporepressor,dimer,Tryptophan,Repressor,dimer,RNApolymerasecannot,bindtothepromoter,Operator,(b)High,tryptophan,:transcriptionisrepressed.,Hightryptophanlevel,Lowlactoselevel,PromoterLeader,-,attenuator,trpE,trpD,Aporepressor,dimer,Tryptophan,Repressor,dimer,RNApolymerasecannot,bindtothepromoter,Operator,(b)High,tryptophan,:transcriptionisrepressed.,LactosetheinducerTryptophantheco-repressor,Inducer诱导物,Co-repressor辅阻遏物,NowshowingThetrpoperon,File:biophoto7LifeThetrpoperon(6),TheTrpOperon:Nopositiveregulation,2.Attenuation/衰减作用,Notalltranscriptionisrepressed.,Attenuator:“STOP!”,Theleader-attenuatorregion前导子-衰减子区域,Theleader-attenuatorRNA,Thecoupledtranscription-translation偶联转录-翻译作用,Whentryptophanlevelislow,Whentryptophanlevelishigh,NowshowingAttenuation,File:biophoto7Genetics:AConceptualApproachAttenuation(10),3.3.4AraandGalOperons3.3.4阿拉伯糖操纵子与半乳糖操纵子,半乳糖,Arabinose阿拉伯糖,1.AraOperon/阿拉伯糖操纵子,AraOperon/阿拉伯糖操纵子,2.G