Prions

[tavaritz]

In his article about prions:

http://www.straightdope.com/columns/...ad-cow-disease

Cecil wrote:

"More importantly, prions reproduce without benefit of DNA or RNA, the only such instance in all of biology."

That's not true. Prions need DNA and RNA, but it's your normal DNA and RNA. Prions have the same aminoacid-chain as a normal protein, but folded wrong way.

So your cells churn up those proteins eg. the aminoacid-chains because there are not enough of them and the all ready excisting prion makes them fold the wrong way, so the new aminoacid-chains also becomes prions.

There is also an additional requirements for prions. That is that there doesn't exist a breakdown mechanism for them.

Normally if an aminoacid-chain folds the wrong way the cell notices it and breaks it down, so that the aminoacids can be reused to make a new aminoacid-chain (and hope they fold the right way).

In cells there are also proteins called scaffolding proteins. The function of these is to facilitate the right folding of other (more complicated) proteins.

Now prions work so that they are scaffolding proteins for themselves. So when ever the cell is making the same aminoacid-chain that can fold into the prion, the prion can facilitate that it folds into a prion. And because there is no breakdown mechanism the prions accumulate.

One of the scariest thoughts I know.