PNA

[Antje]

What is PNA? My bio teacher gave us an article for class and it talked about a DNA like substance called PNA and I just wondered, what is it?

Antje

[Poison]

I do not have an exact info but one of my teacher say that-according to his hypothesis- PRION is the PNA.
PNA: primary nucleic asid

[mbab]

I do not have an exact info but one of my teacher say that-according to his hypothesis- PRION is the PNA.
PNA: primary nucleic asid

you are wrong. PNA ( Peptide nucleic acids), is a nucleic acid mimics in which the sugar phosphate backbone of natural nucleic acid is replaced by a synthetic peptide backbone formed by N-(2_aminoethyl)-glycine units. PNA can recognize DNA and RNA specifically and PNA-DNA, PNA-RNA complexes is more stable than corresponding DNA-DNA, DNA-RNA. PNA is superior to DNA and RNA in recognize single nucleotide polymorphism.

[Poison]

OK. I see. that was not my hypothesis. I only told my teacher's.
Thanx for correcting.

[RobJim]

Do prions have nucleic acid? I thought they were just proteins that catalyzed their own creation. They self replicate, kind of like DNA.

[canalon]

Do prions have nucleic acid? I thought they were just proteins that catalyzed their own creation. They self replicate, kind of like DNA.

Yep, prions have no nucleic acids. Theyr are just proteins.
But they do not self replicate. They catalyze the folding of a protein (itself, but folded differently) made by the cell into another form (the pathogenic, autoreplicative folding).

[thank.darwin]

They catalyze the folding of a protein (itself, but folded differently) made by the cell into another form (the pathogenic, autoreplicative folding).

When you say "folding of a protein" do you mean - they catalyze the folding of a protein by adding bonds, such as disulfide bridges and hydrogen bonds?

[RobJim]

Yep, prions have no nucleic acids. Theyr are just proteins.
But they do not self replicate. They catalyze the folding of a protein (itself, but folded differently) made by the cell into another form (the pathogenic, autoreplicative folding).

I guess they don't assemble the polypeptides like DNA assembles other strands of DNA. They sort of self replicate, but not to the same extent I guess.

[thank.darwin]

What do you mean - "They sort of self replicate , but not to the same extent"
please explain more...

[RobJim]

What do you mean - "They sort of self replicate , but not to the same extent"
please explain more...

Well, DNA can catch and hold nucleotide triphosphates and put them in position to esterify into a new strand of DNA. That is, the DNA can create new molecules of DNA from smaller molecules.

Prions are protein enzymes that catalyze the refolding of other proteins into prion arrangements. Therefore they transform one protein to a prion at a time. However they don't assemble the protein chains from amino acids.

[canalon]

Well, DNA can catch and hold nucleotide triphosphates and put them in position to esterify into a new strand of DNA. That is, the DNA can create new molecules of DNA from smaller molecules.

Prions are protein enzymes that catalyze the refolding of other proteins into prion arrangements. Therefore they transform one protein to a prion at a time. However they don't assemble the protein chains from amino acids.

DNA do not self replicate. It needs quite a complex enzymatic machinery to do so... But, yes, provided the right enzymes it can make a copy of itself. As for prion you need the nucleic acids necessary to produce the protein, then the prion to catalyse the folding of the protein in th eprionic form. A prion cannot be replicated just from itself, the gene coding for the "pre-prion" protein must be present in the cell first.

[abhay]

Prion protein has got two isoforms: PrPc (prion cellular) and PrPSc(prion scrapie).
when we say diseased protein then we are referring it to PrPSc. this protein can change the conformation of PrPc and not any other proteins. one more important thing to keep in mind is that these two proteins have got same DNA sequence.. so its just conformation which makes them different from each other in the terms of proteinase K resistant and infectivity.
as such no other protein has been detected which mediates the above conversion though presence of hypothetical protein X (factor X) has been mentioned in litt.

presence of DNA in this conversion is still highly debated. few researchers are still backing the presence of nucleic acids in scrapie deposits and its role in prion conversion. but "Portein Only" hypothesis given by Stanley B. Prusiner (1997, Nobel Laureate) is still lobbying prion biology. acc. to it, its the scrapie protein which induces conformational change onto normal cellular prion protein.