The proteinaceous particles that lack nucleic acids and are not viruses are termed as prions.
In the healthy brain tissue, the prion proteins are present in the form PrPC, however, in case of prion disease, the normal protein becomes denatured and misfolded and exists in the rogue form which is PrPSc.
The normal form that is PrPC mainly exists in the form of alpha-helices and can bind to copper, however, the rogue form exists mainly in the beta-sheet configuration and is resistant to proteolysis.
Answer: the capsation (the chemical that causes the hot, burning taste/sensation) causes pain and discomfort in the animal attemptng to eat the plant therefor protecting it.
