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2010-10-14 19:29:14
Cellular Molecular biology

Chapter 5 enzymes
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  1. DNA polymerase I
    In prokaryotes, removes and replaces RNA primers (also functions in excision repair of danaged DNA); 3'--> 5' exonuclease (for proofreading);
  2. DNA polymerase II
    In prokaryotes, 3'-->5' exonuclease (for proofreading); repair?
  3. DNA polymerase III
    In prokaryotes, int the main bacterial DNA polymerase for synthesis of the leading stand and of Okazaki fragments by extencion of RNA primers; 3'-->5' exonuclease (for proofreading)
  4. DNA polymerase α
    in Eukaryotes, forms a complex with primase and begins DNA synthesis at 3' end of RNA primers for both leading and lagging strands;3'--> 5' exonuclease (for proofreading)
  5. DNA polymerase ß
    In eukarytoes, for repair
  6. DNA polymerase γ (gamma)
    replication of mitochondrial DNA; 3'-->5' exonuclease (for proofreading)
  7. DNA ploymerase δ
    • In eukaryotes, involved in leading and lagging strand synthesis (also functions in DNA repair);
    • 3'-->5' exonuclease (for proofreading)
  8. DNA polymerase ε
    In eukaryotes, thought to be involved in leading and lagging strand synthesis( also funtions in DNA repair)
  9. DNA primase
    in both cell types, makes RNA oligonucleotides that are used as primers for DNA synthesis
  10. DNA helicase
    unwinds double-stranded DNA via ATP hydrolysis
  11. Single-stranded DNA binding protein
    binds to single-stranded DNA ; stabilizes strands of unwound DNA in an extended configuration that facilitates access by other proteins
  12. DNA topoisomerase (type I and II)
    found in both cell types, makes single-stranded cuts (type I) or double-stranded cuts (type II) in DNA; relaxes DNA supercoiling; can serve as a swivel to prevent overwinding ahead of the DNA replication fork; can seperate linked DNA circles at the end of DNA replication
  13. DNA ligase
    found in both cell types; makes covalent bonds to join together adjacent DNA strands, including okazaki fragments in lagging-strand DNA synthesis and the new and old DNA segments in excision repair of DNA
  14. Initiator Proteins
    In both types of cells, binds to replication of origin and initiate unwinding of the double helix
  15. Telomerase
    using an intergral RNA molecule as a template, synthesizes DNA for extension of telemeres (sequences at ends of chromosomal DNA)