DNA复制的酶学体系徐单单EnzymaticsystemforDNAreplication讲.pptx

DNA复制的酶学体系2主讲老师：徐单单EnzymaticsystemforDNAreplicationGuangdongFoodandDrugVocationalCollege广东食品药品职业学院

DNA聚合酶01DNApolymerase

01DNA聚合酶DNApolymerase

DNA分子结构TheStructureofDNAMolecules全称：依赖DNA的DNA聚合酶(DNA-dependentDNApolymerase)Fullname:DNAdependentDNApolymerase简称：DNA-polAbbreviation:DNApol活性Activity5??3?的聚合活性polymerizationactivity核酸外切酶活性Exonucleaseactivityofnucleicacid5??3?外切活性5??3?exogenousactivity3??5?外切活性3??5?exogenousactivity

DNA-polⅠDNA-polⅠDNA-polⅡDNA-polⅡDNA-polⅢDNA-polⅢ原核细胞中的DNA聚合酶一般有3种TherearegenerallythreetypesofDNApolymerasesinprokaryoticcells

DNA-polⅠ（109kD）功能：对复制中的错误进行校读，对复制和修复中出现的空隙进行填补，切除引物。Function:Itreaderrorsinreplication,fillgapsinreplicationandrepair,removeprimers.5??3?聚合活性5??3?polymerizationactivity5??3?外切活性5??3?polymerizationactivity3??5?外切活性3??5?polymerizationactivity作用特点Functionalcharacteristics

图1.DNA-polⅠ结构Figure1.StructureofDNApolⅠ

DNApolⅠ利用3′→5′外切活性切除错配的碱基，同时利用5′→3′聚合活性补回正确的核苷酸DNApolIutilizes3′→5′exonucleationactivitytoremovemismatchedbases,whileutilizes5′→3′polymerizationactivitytoreplenishthecorrectnucleotides.这种功能称为即时校读(proofread)。Thisfunctioniscalledproofread.

DNApolⅠ的5′→3′外切酶作用可以与其聚合作用同时发生，产生缺口平移、链的置换及模板转辙现象。The5′→3′exonucleaseactionofDNApolⅠcanoccursimultaneouslywithitspolymerization,resultinginnicktranslation,chainsubstitution,andtemplateswitchingphenomena.

图2.DNA-polⅠ发挥校正活性Figure2.DNApolIexhibitscorrectiveactivity碱基配对正确，DNApolⅠ无活性Correctbasepairing,DNApolIinactive3′5′外切活性3??5?polymerizationactivity5′3′聚合活性5??3?polymerizationactivityDNA-polⅠAGdCTPCG5′3′5′3′??

木瓜蛋白酶PapainDNA-polⅠDNA-polⅠN端N-terminalC端C-terminal小片段Smallfragments323个氨基酸323aminoacids5????核酸外切酶活性5????exonucleaseactivity大片段/Klenow片段Largefragment/Klenowfragment604个氨基酸604aminoacids5????聚合活性5????polymerizationactivity???5?核酸外切酶活性???5?polymerizationactivity

Klenowfragmentisacommonlyus