2.1.5   DDDP(DNA聚合酶)

★The first DNA- dependent DNA polymerase (DDDP, DNA-pol I) was discovered in 1958 by Arthur Kornberg -Nobel Prizer of physiology or medicine in 1959. 

(2006 Noble Prizer-his son-Roger Kornberg)

   

                                                                                                                           X ( 1918-2007 )

All of DDDP share the following properties:

★1.Chain elongation: 5'-3 polymerizing （DNA聚合活性）

★2.Processivity  ( 持续性 )

★3.Proofreading: exonuclease  (5’-3’ and/or 3’-5’核酸外切酶活性)

DNA-polof E. coli

          ※ Under the asistance of accessory subunits

DNA-polI

★DNA pol I is not main enzyme in DNA replication

★Genome of E.coli:4×106 bp，20 min for cell division， pol I - 24h.

★Mainly responsible for proofreading (校读)and cleaving primer(切除引物), filling the gaps（填补空隙）, repairing DNA damage（修复DNA损伤）

Klenow fragment

★small fragment –小片段 (323 AA): 5´→3´ exonuclease activity

★large fragment-大片段 (604 AA): Klenow fragment, DNA polymerization and 3´→5´exonuclease activity

★Tool enzyme in scientific research.

DNA-pol   Ⅲ

★With highest elongation rate and most processive ability

★A heterodimer enzyme composed of ten different subunits: core enzyme(核心酶) + γ complex (γ复合体)

★The major enzyme responsible for the elongation process

           β：clamp, binding template (结合模板并滑动, In eu: PCNA )。 

               γ complex: loading β subunit (引导β亚基与 模板的结合, In eu: RP-C) 

DNA-pol Ⅱ, IV and V

★DNA pol Ⅱ: Not know much 

★DNA pol IV and V was discovered in 1999 .

★Responsible for replication when DNA is seriously damaged. ( DNA严重损伤时起作用)

★Fidelity is bad due to incomplete template.

DNA-pol in eukaryotes(真核细胞)

DNA-pol in eukaryotes

  

    Mg2+ isnecessary for DNA polymerase activity.