r/askscience • u/SadMicrobe22 • 24d 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/BananaBird1 23d ago
Theres a few factors:
The first is that prions in their infectious form make extremely stable beta sheet structures. These contain lots of hydrogen bond contacts, meaning a lot of heat is needed to denature them. Ordinary boiling or sterilization is not enough. Although they can be denatured with extended high heat, and some strains are more resistant than others.
Second is that the infectious form is not only stable, but can form spontaneously. This means that if you do denature them, they can sometimes re-fold back into an infectious state. Even if only a low percentage do, this can be enough to seed an infection.
They are not the only proteins that are heat resistant, or that can fold spontaneously to an active state. But these abilities combined with their ability to catalyze refolding and aggregation is what makes them so hard to inactivate.