Thursday, June 18, 2009

I'm an enzyme!

Being a science nerd means you get to have fun alll the time. We get joy out of many different activities and discoveries. For example, writing out mad libs but instead of words and letters, using the chemical structures of amino acids and their one letter substitutions as code. Other times it's fun to see who can read a long sequence of DNA the fastest, and then who can read the antisense mRNA the fastest ... without writing it down!

But today, I thought I'd share with you the joy of having my own restriction endonuclease named after me. Well, not exactly named after me, but it has the same initials as me - elevating me to cool status. What restriction enzyme do I share my initials with???

Answer: MscI

If you're not aware, restriction enzymes are like scissors, but in chemical form. They take long strings of DNA and cut at sequence specific sites. For example, if you had the DNA sequence 5'-GATCTAGGAATTCTCTAG-3' then at that bold spot, the restriction enzyme EcoRI could cut that DNA, separating it into two pieces. Cool, huh? But remember, DNA is double stranded; so when it cuts, it looks like this:

Those leftover sticky ends want to bind again, and will, if they're given other pieces with complementary sticky ends. So think about it ... if we can harness the power of these enzymes, then we can cut and paste different pieces of DNA together in any order we want! This is what scientists discovered in the 1970s and ultimately lead to the era of genetic engineering. We've come a long ways since then, but that's basically the gist. Using restriction enzymes we cut up pieces of DNA and insert in pieces that we want and then put the whole construct in an organism of interest to be expressed. Shazam! You've got a genetically engineered organism.

These enzymes were originally discovered in bacteria as a defense mechanism against foreign pieces of DNA from invading viruses and other sources. Remember, if bacteria exchange genetic information then they're having a form of sex and they don't want to do that with just anything. There are many of these enzymes out there that have been discovered, and each one cuts only at its sequence specific site. Interestingly, all restriction enzyme sites are palindromes, or they are the same sequence forward as they are backwards. So using our host of enzymes, we can cut and paste our way into the genetics of the future.

I wonder what properties I share with my restriction enzyme ... ? According to New England Biolabs I work at 75% in Buffers 1, 2, and 3, and at 100% in Buffer 4. I'm not sensitive to methylation or CpG methylation, but with dcm methylation I am blocked by overlapping. You can heat inactivate me at 65 degrees Celsius for 20 minutes but I work optimally at 37 degrees Celsius. I'm an isochizomer of BalI and if I'm not working well, just give me a little more KCl and I'll get the job done.

Does that turn you on?

1 comment:

John and Caitlin said...

I'm designing a new virus for my work. To help myself out during the cloning process, I decided to engineer my primer to encode a restriction enzyme site, allowing me to screen a hell of a lot easier. The only enzyme that worked? MscI. True story. Hope life is treating you well, Mamew. :)