[CrazCo]

makes absolutely zero sense to me how a misfolded protein without any instruction from nucleic acid can infect cells. can someone help?

[Moontanman]

This explains it much better than I ever could

http://en.wikipedia.org/wiki/Prion

[dttom]

Imagine there is a vesicle holding 100 sucrose, one disaccharase comes in, and break sucrose up to glucose and fructose, vesicle membrane can't withstand the osmotic pressure and burst, that disaccharase bursts out and moves to another sucrose vesicle...

What if you consider that disaccharase as an enzyme catalysing production of itself? What if the product are not glucose and fructose but disaccharase itself?

[Genecks]

In general, imagine that you have a ball and a cube. The cube is the regular shape of the good protein. The ball is the shape of the prion. The prion has the ability to change the cube into a ball. A cube's shape is energetically unstable, and it wants to shape into something more stable: In this case, the ball is the more stable shape. The prion touches the normal protein, and the normal protein turns into a ball.

Yes, this issue can be perplexing. Please note that in this situation, a prion could be interpreted as an information-containing molecule, which is against the norm of what people consider to be biological information molecules.

[CharonY]

Sorry this is not true. Folding is not considered information containing as it just alters the state of the protein/prion in question. For the same reasons you would not consider the substrate in e.g. allosteric inhibition as information.
Moreover the misfolded prion is not more stable than the other form. If that was the case there would only be misfolded protein. Both states are stable but the misfolded prions facilitate the conversion from one state to the other.

[Genecks]

I guess you're right, CharonY.
Sorry about the misinformation, original poster.

[ecoli]

Genecks said:

I guess you're right, CharonY.
Sorry about the misinformation, original poster.

The mechanism of replication is not yet clear, but something is driving the "re-folding" reaction forward. Two, seemingly good, theories are template-directing refolding of normal proteins and self-propagating aggregation.

[CharonY]

From what I remember the aggregation of misfolded prions pertains to the onset of the diseases but is not a crucial factor in driving the conformational changes itself. Once in the infectious form, they rapidly aggregate (but not before).

[ecoli]

CharonY said:

From what I remember the aggregation of misfolded prions pertains to the onset of the diseases but is not a crucial factor in driving the conformational changes itself. Once in the infectious form, they rapidly aggregate (but not before).

hmm... I was under the impression that they form infectious particles after aggregation. Could there be differences in this regard between the animal and yeast models?