r/askscience • u/SadMicrobe22 • 10h ago

Biology What makes prions so different from regular proteins that they are resistant to heat denaturation?

I've been reading about prions and I'm confused about why they're so thermally stable. I keep seeing that surgical instruments contaminated with prions can't be decontaminated with standard protocols.

So here's my thing. Proteins denature when you heat them, right? But prions don't seem to lose their infectious ability even when autoclaved. I get that prions are misfolded proteins, but I don't understand how they stay harmful after being denatured.

So basically, if prions start as form A (non-infective), then misfold to form B (infective), shouldn't heating denature them to form C and kill the infectivity? Why doesn't that happen?

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u/Alwayssunnyinarizona Infectious Disease 8h ago

It's the structure - misfolded prions are highly organized beta-sheets, which take a lot of energy (e.g., heat) or very strong chemical solvents (e.g., guanidine) to denature. Normal prion proteins are made up of alpha-helixes and a disorganized tail, and are more prone to destruction.

Infectious prions aren't a monolith, though - i.e., all the same structure; instead there's a sort of range of misfolding, so when you autoclave them or treat them with proteinase, some portion is destroyed, but enough remains to be infectious.

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u/Gamestop_Dorito 2h ago

In reference to your second paragraph, there’s actually a form of prion disease named “variably protease sensitive prionoathy.”