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Topic: Why they are so many DNA polymerase?  (Read 10705 times)

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Offline studytogether

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Why they are so many DNA polymerase?
« on: April 29, 2008, 05:59:30 AM »
my textbook states that:

Nevirapine binds bdirectly to HIV-1 reverse transcriptase; thus, it blocks RNA- and DNA-dependent polymerase.

Question 1 :
does it means that: reverse transcriptase may be RNA- or DNA-dependent polymerase?

and it also states that nevirapine doesn't inhibit HIV-2 reverse transcriptase and human DNA polymerase.

Question 2 :
It means that: HIV-2 reverse transcriptase and human DNA polymerase are not RNA- or DNA-dependent polymerase?
 
thx 4 teaching ::)

Offline Arkcon

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Re: Why they are so many DNA polymerase?
« Reply #1 on: April 29, 2008, 06:38:35 AM »
Question 2 :
It means that: HIV-2 reverse transcriptase and human DNA polymerase are not RNA- or DNA-dependent polymerase?

No, there is a more likely reason for why the small (well, relatively) molecule pharmaceutical nevirapine is selective for the HIV-1 reverse polymerase.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline studytogether

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Re: Why they are so many DNA polymerase?
« Reply #2 on: April 29, 2008, 07:22:29 AM »
can u tell me that :HIV-2 reverse transcriptase and human DNA polymerase are RNA- or DNA-dependent polymerase or not?

and I want to know what is RNA- or DNA-dependent polymerase? Is there RNA- or DNA-independent polymerase?

and what is the classification of HIV-1 reverse transcriptase and  HIV-2 reverse transcriptase and human DNA polymerase ?

Offline Arkcon

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Re: Why they are so many DNA polymerase?
« Reply #3 on: April 29, 2008, 09:23:05 AM »
That would depend on the answer in your textbook or class notes.  FWIW, there's a new term "Template Dependant Polymerase", as a catch all term for polymerases that use either a DNA or RNA template, to make a complementary stand.  Here's an example of a eukaryotic template independent polymerase -- http://en.wikipedia.org/wiki/Terminal_Deoxynucleotidyl_Transferase
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Yggdrasil

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Re: Why they are so many DNA polymerase?
« Reply #4 on: April 29, 2008, 08:31:38 PM »
Polymerases can be classified by the type of nucleic acid they produce (DNA or RNA) and the type of template they require (DNA, RNA, or no template).  A DNA-dependent DNA polymerase is a protein that synthesizes DNA on a DNA template.  An example of this type of enzyme is DNA polymerase delta, the main DNA polymerase responsible for replicating DNA in eukaryotes.  As the name implies, an RNA-dependent DNA polymerase synthesizes a strand of DNA using an RNA template.

Viruses are interesting to biologists in part because their genomes are very small and they therefore can make a limited number of proteins.  Thus, viruses have to be efficient and many of their proteins can perform roles that are normally performed by a number of different proteins in prokaryotes or eukaryotes.  HIV reverste transcriptase (RT) is one such example.

RT has three different enzymatic activities.  It is has RNA-dependent DNA polymerase activity, DNA-dependent DNA polymerase activity, and RNase H activity (it degrades RNA in an RNA/DNA hybrid structure).  All three activities are required for HIV to convert its single-stranded RNA genome into a double stranded DNA for integration into the host's genome.  An interesting question in the field of polymerase enzymology is how RT switches between these different activities.  Although it is not published yet, some really single molecule experiments have proposed that RT does "gymnastics" on its DNA or RNA substrate, physically flipping itself around to switch between these different activities.

Offline studytogether

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Re: Why they are so many DNA polymerase?
« Reply #5 on: April 30, 2008, 05:10:03 AM »
virus is harm for man because their reproduction leads to lysosis and the protein they creat often cause immunoreaction?

is the "protein they creat" means the virus itself? or particle besides virus itself? or protein on virus itself?

Offline Yggdrasil

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Re: Why they are so many DNA polymerase?
« Reply #6 on: April 30, 2008, 04:24:56 PM »
Yes.  Viruses are harmful because they use up a cells' resources in order to replicate themselves and eventually lyse the cells.  Some viruses can cause additional harm though various other means.  For example, human paploma virus (HPV) is known to cause cancer because it inactivates various proteins in the cell that protect the body from viral infection.  Unfortunately, the proteins that HPV inactivates are also involved in protecting the cell from cancer.

The genomes of viruses encode a number of proteins.  Some are involved in viral replication (e.g. HIV RT and HIV integrase), others are components of the virus itself (e.g. capsid protein), and others are involved in the infection process (e.g. the HPV proteins that inactivate our tumor suppressor genes).

Offline studytogether

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Re: Why they are so many DNA polymerase?
« Reply #7 on: May 01, 2008, 07:49:02 AM »
thx u very much :D

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