Drybench Plasmid.
Restriction enzymes and their sites
A restriction enzyme recognises a short DNA sequence, its site, and cuts both strands at a fixed place in or near it.
Sites and cuts
The first site-specific restriction enzyme was purified from Haemophilus influenzae (Smith and Wilcox 1970). Enzymes are named for the bacterium they come from, with a Roman numeral for the order of discovery (Roberts et al. 2003).
Many sites read the same on both strands, such as EcoRI's GAATTC. Where the two strands are cut at different places the ends overhang, as sticky ends that pair with any end made by the same enzyme; where they are cut at the same place the ends are blunt.
Type IIS enzymes
Type IIS enzymes such as BsaI cut a fixed distance outside their site, on one side (Szybalski et al. 1991). The overhang they leave can be any sequence, which is what Golden Gate cloning uses; on a linear molecule a Type IIS site near an end can cut off the end altogether.
This site's table lists each enzyme's site and its cut on each strand, typed by hand and checked, enzyme by enzyme, against an independent program on pUC19 and pBR322.
See it on a real plasmid
Open pUC19 and look at the unique cutters in its cloning site.
Restriction enzymes read the bases of the double helix; the tour's first stop shows DNA itself.
References
- Smith HO, Wilcox KW. A restriction enzyme from Hemophilus influenzae. I. Purification and general properties. J Mol Biol 1970;51:379-391. PubMed 5312500
- Roberts RJ, Belfort M, Bestor T, et al. A nomenclature for restriction enzymes, DNA methyltransferases, homing endonucleases and their genes. Nucleic Acids Res 2003;31:1805-1812. PubMed 12654995
- Szybalski W, Kim SC, Hasan N, Podhajska AJ. Class-IIS restriction enzymes: a review. Gene 1991;100:13-26. PubMed 2055464
Statements summarised by the site's builder from the references, for scientific review.