TABLE 25-1 Comparison of DNA Polymerases of E coli DNA polymerase Structural gene A1 polB poic(dnaE) Subunits(number of different types ≥10 103,000 88000t 791500 3→5′ Exonuclease( proofreading Ye 5′→3′ Exonuclease Yes Polymerization rate (nucleotides/s) 16-20 250-1,000 Processivity(nucleotides added 3-200 1500 ≥500.000 before polymerase dissociates) More than 90 of the dna polymerase activity observed in E. coli extracts can be accounted for by dna polymerase I
More than 90 % of the DNA polymerase activity observed in E. coli extracts can be accounted for by DNA polymerase I
(四)参与复制的酶和蛋白质 DNA的复制 TABLE 25-2 Subunits of DNA Polymerase Ill of E. coli Number of subunits per Subunit holoenzyme Mr of subunit Gene Function of subunit 2222 129, 900 poic(dnae) Polymerization activity 27,500 dnaQ(mutD) 3'5' Proofreading exonuclease Core polymerase 8,600 ho/e 71,100 dnaX Stable template binding core enzyme dimerization Clamp-loading (y) complex that 47,500 ana Clamp loader loads B subunits on lagging y68xi 38.700 holA Clamp opener strand at each Okazaki fragment 36,900 Clamp loader 16600 ho/C Interaction with SSB 15,200 holD Interaction with y and x 40.600 DNA clamp required for ptimal processivity DNA polymerase Ill is much more complex than dNA polymerase I, having ten types of subunits
(四)参与复制的酶和蛋白质 一.DNA的复制 DNA polymerase III is much more complex than DNA polymerase I, having ten types of subunits
(四)参与复制的酶和蛋白质 DNA的复制 Core(aee B clamp 0 B clamp (open) DnaB helicase
(四)参与复制的酶和蛋白质 一.DNA的复制
(四)参与复制的酶和蛋白质 DNA的复制 2.DNA聚合酶( DNA polymease) 催化活性 DNA聚合酶5→33→55→3 功能 聚合核酸外切核酸外切 DNA聚合 切去引物RNA,补 妈号o 上正确的DNA片段 真 DNA聚合 酶β 核生 DNA聚合 酶y 负责链的延长 物 DNA聚合 酶δ 十 负责先导链的延长
DNA聚合酶 催化活性 5'→3' 功 能 聚合 3'→5' 核酸外切 5'→3' 核酸外切 真 核 生 物 DNA聚合 酶a ＋ 切去引物RNA，补 上正确的DNA片段 DNA聚合 酶b ＋ DNA聚合 酶g ＋ 负责链的延长 DNA聚合 酶d ＋ ＋ 负责先导链的延长 (四)参与复制的酶和蛋白质 一.DNA的复制 2. DNA聚合酶(DNA polymease)
(四)参与复制的酶和蛋白质 DNA的复制 2.DNA聚合酶 DNA polymease) 5 Primer strand.· O CH Base::·Base OH O一P-0—P一O O CH. B OH
( 四 )参与复制的酶和蛋白质 一 .DNA的复制 2. DNA聚合酶 (DNA polymease)