Many different forms of DNA Helicase exist in the world, with slight differences in structure generally occurring between species of living organisms (shown below). Most of the crystal structures of helicases that have been solved so far have come from small bacteria or yeast, where it's easiest to isolate the one specific enzyme. But despite these different forms and structures, all forms of DNA Helicase have the same, very important job. It uses the energy from hydrolysis of ATP to break the many hydrogen bonds that form between base pairs of the nucleic acids that make up DNA and keep it held together in its classic double-helical shape.
Bacteriophage T7 DNA helicase crystal structures
The products of the "reaction" then are single strands of DNA that have been unzipped and can then be replicated by other enzymes.
We never really give much thought to how much work our proteins do inside our bodies, and rarely do we recognize them at all unless something goes wrong. But when we think about DNA helicase, this one tiny protein that is an integral part of all living organisms, it's an incredible thought. This enzyme has been working since the very moment our cells began replicating, and without it, we wouldn't have made it past one cell! Not one organism on earth would be alive were it not for this motor enzyme moving along the backbone of the nucleic acids that make up our DNA. And even though most DNA replication errors occur later down the line, DNA helicase still has a pretty impressive record for how few mistakes it makes. This protein is essential for multicellular life to happen and be sustained. Be thankful for DNA Helicase!
A proposed mechanism for how DNA helicase works can be seen at
http://www.youtube.com/watch?v=UWNhwceMjfk
References
1. Foadey, Wilfried. DNA Helicase: Function/Role. N.p., 5 Nov. 2004. Web. 26 Apr. 2011 <http://www.cs.stedwards.edu/chem/Chemistry/CHEM43/CHEM43/Projects04/HELICASE/FUNCTION.html>.
2. "Helicase." Wikipedia: The Free Encyclopedia. N.p., 28 Mar. 2011. Web. 26 Apr. 2011. <http://en.wikipedia.org/wiki/Helicase>.
3. Lionnet, Timothee, Michelle M. Spiering, Stephen J. Benkovic, David Bensimon, and Vincent Croquette. "Real-time observation of bacteriophage T4 gp41 helicase reveals an unwinding mechanism." Proc Natl Acad Sci USA 104.505 Dec. (2007): 19790-95. Web. 26 Apr. 2011. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2148377/?tool=pmcentrez>.
This is a great enzyme. I agree with your statement that without DNA helicase, we would not be able to replicate our cells and life would not go on. Thank you for sharing the wonders of this protein.
ReplyDeleteNice work. I especially like the Pymol representation at the end. You did a good job making the separate protein and DNA parts clear.
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