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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. (From Tock and Dryden 2005). Type I. Three subunits form R 2 M 2 S 1

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restriction enzymes

Restriction Enzymes

Presented by: Elizabeth Gordon

April 11,2006

function
Function

(From Tock and Dryden 2005)

historical perspective
Historical Perspective

(From Lewin 2003)

four types
Four Types

(From Tock and Dryden 2005)

type i
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
type ii
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
type iii
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
type iv
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
homing endonucleases
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
anti restriction strategies pt 1
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
anti restriction strategies pt 2
Anti-Restriction Strategies Pt 2
  • Stimulation of restriction-methylation system
  • Depletion of intracellular co-factors
  • Phage-encoded proteins
  • Plasmid-encoded proteins
future research
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
literature cited
Literature Cited
  • Belfort, M and Roberts, RJ. “Homing endonucleases: Keeping the house in order.” Nucleic Acids Research. 1997. 25, 17:3379-3388
  • Tock, MR and Dryden, DTF. “The biology of restriction and anti-restriction.” Current Opinion in Microbiology. 2005. 8:466-472
  • Lewin, B. Genes VII. Prentice Hall. 2003.
  • Van Valen L. “A New Evolutionary Law.” Evolutionary Theory 1973. 1, 1-30