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Restriction Enzymes

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Restriction Enzymes Presented by: Elizabeth Gordon April 11,2006 Function (From Tock and Dryden 2005) Historical Perspective (From Lewin 2003) Four Types ... – PowerPoint PPT presentation

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Title: Restriction Enzymes


1
Restriction Enzymes
  • Presented by Elizabeth Gordon
  • April 11,2006

2
Function
  • (From Tock and Dryden 2005)

3
Historical Perspective
  • (From Lewin 2003)

4
Four Types
  • (From Tock and Dryden 2005)

5
Type I
  • Three subunits form R2M2S1
  • Restriction endonuclease, methyltransferase, and
    ATPase activities
  • Requires ATP, SAM, and Mg2
  • Asymmetric, two-part sequence
  • Cleaves approximately 1KB away from recognition
    site
  • Can be used for DNA Translocation

6
Type II
  • Two different subunits form R2 or M1
  • Restriction endonuclease or methyltransferase
  • Requires SAM and Mg2
  • Mostly symmetric recognition site
  • Cleaves at or near site
  • No DNA translocation capacity

7
Type III
  • Two different subunits form mod2res2
  • Restriction endonuclease, methyltransferase, and
    ATPase activities
  • Requires ATP, SAM, and Mg2
  • Asymmetric
  • Cleaves 25-27 bp away from the recognition site
  • DNA translocation capability

8
Type IV
  • Two subunits McrB, McrC
  • Restriction endonuclease and GTPase
  • Requires GTP and Mg2
  • No methylation activity
  • Recognition sequence is two-part and methylated
  • Cleaves between methylated bases
  • Can assist in DNA translocation

9
Homing Endonucleases
  • Used to create introns
  • Create double stranded breaks
  • Insert into intronless alleles
  • Cleave at a specific sequence
  • Recognize 12-40 bp sequences
  • Can form RNP complexes

10
Red Queen Principle
11
Anti-Restriction Strategies Pt 1
  • Loss of restriction and methylation recognition
    sites
  • Strand-biased asymmetrical recognition sequences
  • Incorporation of unusual bases into phage genomes
  • Phage-encoded DNA-modifying enzymes

12
Anti-Restriction Strategies Pt 2
  • Stimulation of restriction-methylation system
  • Depletion of intracellular co-factors
  • Phage-encoded proteins
  • Plasmid-encoded proteins

13
Future Research
  • Use of anti-restriction to treat bacterial
    pathogens
  • Studying the role of Homing Endonucleases in the
    creation of introns
  • Exploring any possible unknown categories of
    restriction enzymes

14
Questions?
15
Literature Cited
  • Belfort, M and Roberts, RJ. Homing
    endonucleases Keeping the house in order.
    Nucleic Acids Research. 1997. 25, 173379-3388
  • Tock, MR and Dryden, DTF. The biology of
    restriction and anti-restriction. Current
    Opinion in Microbiology. 2005. 8466-472
  • Lewin, B. Genes VII. Prentice Hall. 2003.
  • Van Valen L. A New Evolutionary Law.
    Evolutionary Theory 1973. 1, 1-30
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