Prion protein (PrP) !

The normal prion protein sits on neurons; its misfolded form turns the others into copies of itself and destroys the brain.

Updated 2026-11-01

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Key facts

PRNP gene (chromosome 20); normal PrPC is a GPI-anchored membrane glycoprotein, rich in α-helices.
PrPSc (the disease form) is rich in β-sheets, resists proteases and acts as a template: it converts PrPC into more PrPSc.
It is the only known transmissible disease caused by a protein alone, with no nucleic acid.
The codon 129 polymorphism (methionine/valine) changes susceptibility: Met/Met homozygotes are more vulnerable.
PrPSc resists usual sterilisation (dry heat, formalin, radiation); special protocols are needed.

Structure 1QLX is normal human PrP (cellular form) solved by NMR: a flexible N-terminal tail and a globular domain with three α-helices and a small β-sheet.
There is no simple atomic structure of full-length PrPSc; in it much of the helical content turns into β-sheet.

Strongly expressed in neurons; its normal role is not fully clear (copper binding, myelin maintenance, synaptic signalling).
PRNP variants (for example E200K, D178N) favour the switch to the disease form.

No drug that blocks conversion has proven benefit in people
Decontamination with concentrated sodium hydroxide or hypochlorite and prolonged autoclaving inactivates PrPSc

Creutzfeldt–Jakob disease: sporadic (the commonest), genetic and iatrogenic; variant CJD (vCJD) from eating beef with bovine spongiform encephalopathy.
Features: dementia progressing over weeks to months, myoclonus and ataxia; tissue shows spongiform change without inflammation.
The RT-QuIC test on cerebrospinal fluid detects PrPSc's ability to seed new fibres.

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How does PrPSc differ from PrPC?

Same sequence, but folded with much β-sheet; it resists proteases and converts PrPC into more PrPSc.

Which PRNP polymorphism affects prion susceptibility?

Codon 129: methionine/methionine homozygotes are at higher risk, and nearly all vCJD cases are.

Why can surgical instruments transmit prions?

PrPSc resists the usual dry heat, formalin and radiation; special decontamination protocols are needed.

Which cerebrospinal fluid test detects prions with high specificity?

RT-QuIC, which amplifies PrPSc's ability to convert normal protein into fibres.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: PRNP: Major prion protein (human) (UniProt, 2026); PRNP gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); 1QLX: Human prion protein (RCSB Protein Data Bank, 2026); Prion disease: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Representative model, for educational purposes only.