生化课件2dnabiosynthesis教学教材.ppt

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1、生化课件2DNABiosynthesis2017KlenowfragmentA-Fsegments(323AA):thesmallfragment,having5´→3´exonucleaseactivityG-Rsegments(604AA):thelargefragmentcalledKlenowfragment,havingDNApolymeraseand3´→5´exonucleaseactivity,ausefultoolenzymeNendCendcaroidDNA-polⅠ3´→5´exonucleaseactivityexcisemismatc

2、hednuleotides5´→3´exonucleaseactivitycutprimerorexcisemutatedsegment？ExonucleaseActivitiesofDNAPol.ITwometalionsparticipateintheactivesiteofDNApolymerase.KlenowFragmentPolymerizationcenterBaseSelectionofDNApolymerasesTworesiduesofDNApolymerasesinteractwithminorgroovebytwohydrogenbon

3、dstowatson-crickbasepairintheactivesite.BaseSelectionofDNApolymerasesOnlythepropershapedbasepairswillreadilyfitthetightpocket.DNA-polofE.coliDNA-polIIIThecoreenzymeα5´→3´polymeraseε3´→5´exonucleasebaseselectionθheterodimerizationsubunits“clamp”-complexεεTheβ2serveasaslidingDNAclam

4、p.DNA-polinprocaryotesDNA-polIDNA-polIIDNA-polIII5’→3’polymeraseYesYesYes3’→5’exonucleaseYesYesYes5’→3’exonucleaseYesNoNoFunctionEraseprimers,fillgapsforrepairandreplicationDNArepairElongatetheDNAstrandsandproofreadduringreplicationDNA-polinEukaryotesDNA-pol:elongationDNA-polIIIHel

5、icaseDNA-pol:initiatereplicationandsynthesizeprimersDnaG,primaseDNA-pol:replicationwithalowfidelityDNA-pol:DNAreplicationinmitochondriaDNA-pol:proofreadingandgapfillingDNA-polISOSRepairDNA-polIIHelicaseinE.coliDnaBItopensthedoublestrandDNAwithATPconsumption.ItneedsthehelpfromDna

6、AandDnaC.DnaA-recognizetheoriginDnaC-transportandassistDnaBPcrAcontainsfourdomainsA1,A2,B1,B2.ATPbindingtoA1closesthecleft.ThenATPhydrolysispushesB1andB2towardsthedoublestrandedpartandthecleftopenupagain.HelicasesPcrAhydrolyzeATPtopowerthestrandseparation.TheHexamericHelicasefromBac

7、teriophageT7DDDDSSBprotein((SinglestrandDNAbindingprotein,SSB)maybindandstablizeDNAinthesingle-strandform.PreventthedsDNAformation.ProtectthevulnerablessDNAfromnucleases.PrimasescatalyzethesynthesisofRNAprimer.DnaGinEColiUsingfreeNTPstosynthesizeshortRNAprimers.DNALigasessealthebrea

8、k.NecessaryforRepli