The Eureka Enzyme!

DNA polymerase hard at work in the cell!
Photo from accentsrq.com

   Imagine this: it is 12 AM, and you are just starting the ten page research paper you’ve known about for weeks merely eight hours before it is due. Sweat drops on the keyboard as your fingers glide across the keyboard, there is no time to waste, but can you guarantee you will not make any grammatical errors along the way? Is there such thing as an organism/molecule that can work at a speedy pace AND make minimal, if any, errors? DNA polymerase I can! The enzyme works at adding 16-20 nucleotides/s to a new DNA strand in E.coli, which is slow for a polymerase. Its fellow isozyme, DNA polymerase III, can add 250-1,000 nucleotides/s in E. coli!

View down the double helix

   The accuracy of DNA polymerase enzyme is remarkable, research has shown it inserts an incorrect base pair every 104-105 bases in eukaryotes. Not impressed? DNA polymerase is also its own editor! It has proofreading capabilities and inhibits the addition of a nucleotide following a mismatch, increasing the accuracy of DNA polymerase 102-103 fold. Spell check cannot compare. If one factors in the enzyme’s proofreading capabilities, the enzyme makes an error every 106 to 108 base pairs!

   Textbook version of DNA polymerase activity
Photo from worldofscience.blogcu.com

   Still not convinced DNA polymerase is the shizz? Think you could live without it? Think again. If a nucleotide mismatch goes unrepaired, known as a mutation, it can go unnoticed in the organism, dubbed a silent mutation, or it can be deleterious to the organism. This single nucleotide change alters only one amino acid in the protein chain, but the results are devastating. One of the most well known example of a point mutation is sickle-cell anemia, and without daily treatment the average life expectancy of the patient is 20-40 years.

Double helix in stick display in rainbow coloring

   There has also been strong evidence linking cancer and the amount of mutations in mammals. You know how you are always told to wear sunscreen while basking in the sunshine? This is why; UV light induces the formation of dimers within DNA and contributes to the 10 percent of all DNA damages caused by environmental factors. Dimers cause kinks and bends in DNA, which results in permanent damage. This can ultimately lead to skin cancer, the number one form of cancer in the United States. DNA polymerase is also an important target for anti-viral drugs, as DNA viruses program their own DNA polymerases. This has been used to combat viruses such as herpes, which infects 16.2 percent of the U.S. population, or about one out of six, people 14-49 years of age.

Pretty.

     DNA polymerase was destined for great things since its discovery in 1956. It was coined the “eureka” enzyme before all of its fundamental roles in life were revealed. Without this enzyme, life as we know it would cease to exist. As the late John Calvin once said, “DNA is life, the rest is just details.”


References:
Genital Herpes. CDC, Dec. 2007. Web. 25 Apr. 2011.

<http://www.cdc.gov/std/herpes/herpes-fact-sheet-lowres-2010.pdf>.

Goodshell, David S. RCSB Protein Data Bank. N.p., Mar. 2000. Web. 17 Mar. 2000.

<http://www.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb3_2.html>.

Nelson, David L., and Michael M. Cox. Principles of Biochemistry. 5th ed. New York:

W.H. Freeman and Company, 2008. 979-982. Print.

Nelson, David L., and Michael M. Cox. Principles of Biochemistry. 5th ed. New York:

W.H. Freeman and Company, 2008. 289-290. Print.

Sickle cell anemia. Ed. Linda Vorvick, Yi-Bin Chen, and David Zieve. A.D.A.M., 31 Jan. 2010.

Web. 25 Apr. 2011. <http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001554/>.

Skin Cancer. CDC, 23 March 2010. Web. 25 Apr. 2011.

<http://www.cdc.gov/cancer/skin/basic_info/>.