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Question for experts: Helicases

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Question for experts: Helicases

Postby AFJ » Sat Jul 04, 2009 2:34 pm

Can anyone explain to me how the helicase process in strand separation is possible as far as time? Are there several helicases taking each a portion of the DNA, or does one start at one end and split the entire strand? If the latter is the case, how does it separate 3 billion nucleotides in reference to time?
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Postby Jesse2504 » Sat Jul 04, 2009 7:11 pm

Helicase is part of the protein complex that replicates DNA. DNA replication begins by a "bubble" forming in the molecule where the first few hydrogen bonds between complementary base pairs are broken opening the DNA molecule for replication. From here Helicase works in both directions opening the DNA molecule. Many bubbles can form in a single DNA molecule which speeds up the process.

The speed of Helicase depends on certain conditions such as temperature and other necessities as you would expect, if you look you can probably find an estimate for its nucleotide per second speed.
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Re: Question for experts: Helicases

Postby AFJ » Sat Jul 04, 2009 8:47 pm

From here Helicase works in both directions opening the DNA molecule.

How? Does it split in two, or are there more helicases that enter into the picture. The only thing I can find is that it makes a fork in the DNA and a really cheap animation. Maybe they don't really know in detail. Anyway it amazes me that one could handle 3b nucleotides before cell death.
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Postby kolean » Sat Jul 04, 2009 11:03 pm

Here is a link to a free access on PubMed about several different kinds of helicases:
http://www.pubmedcentral.nih.gov/articl ... d=18329872

In a human/eukaryotic cell, there are multiple origins of DNA replication. Helicases are part of the whole DNA synthesis initiation and elongation process. Using ATP, they are able to pull the base pairs apart from the SSB proteins that has "straightened out" the DNA helix for the helicase to do its job. Thus each initiation to elongation complex has the helicase on board working to pull the DNA base pairs apart.
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Re: Question for experts: Helicases

Postby AFJ » Wed Jul 08, 2009 2:13 am

Thanks kolean
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