Molecular Scissors: Restriction Enzymes
✄ Microbial Underworld: Imagine a cut throat, competitive underworld where intruders are efficiently decimated by a custom-made weapon that slashes right through their life lines. These ancient molecular scissors evolved in bacteria to defend against parasitic viruses, called ‘phages. Better known as restriction endonucleases, these enzymes recognize a specific DNA sequence as their target. A short 6-8 letter sequence effectively marks the hapless victim for destruction. How does the host go unscathed? The same sequence is protected by a chemical modification (methylation) that makes it invisible to a veritable incarnation of Edward Scissorhands.
✄ Snip, Snip! The molecular scissors are named after the bacteria of origin. For example, Eco RI signifies that it was from the E. coli bacterium. Several thousand have been discovered, that recognize some 200 unique sequences. A favorite of the biologist’s tool kit recognizes palindromic sequences, that read the same forward or backward.
Here’s one, that snips straight through (cuts indicated by |), making blunt ends:
Here’s another that makes a staggered cut, better known as sticky ends:
✄ Nobel Find: The scientists who discovered restriction endonucleases (two from my home ground, Dan Nathans and Ham Smith, along with Werner Arbor) were honored with the Nobel prize. These molecular scissors gave birth to new fields of Recombinant DNA technology and more recently, Synthetic Biology. We can now cut and paste genes, clone and copy them, and move them in or out of cells, thanks to these precise cutting tools (together with handy glue in the form of ligases or joining enzymes).
Image: Eco RI wrapped around model DNA, by John M. Rosenberg via http://goo.gl/OGb5N
This post is to celebrate the birthday of Kawthar AL ABDALLA , who is beautiful both inside and out. Watch out, Kawthar uses ✄ as effectively as a restriction enzyme!
#KKScissorHands #whatever #HappyBirthdayKawthar #ScienceEveryday