Question

Do prions have proteins?

Answer 1

Proteins are big biomolecules or macromolecules made up of one or more long chains of amino acid residues. Prions are the hallmarks of a number of lethal and transmissible neurodegenerative diseases that affect humans and a variety of other species.

Complete answer:
Prions are misfolded proteins with the ability to infect regular variants of the same protein with their misfolded form. A prion is a protein that causes disease in both animals and humans by causing normally healthy proteins in the brain to fold abnormally.

The mode of action of prion is very different from that of bacteria and viruses because they are simply proteins with no genetic material. When a misfolded prion enters a healthy person – possibly through infected food – it converts correctly-folded proteins to the disease-associated form. Nobody knows exactly how this happens to this day.

The word "prion" refers to the pathogen that causes transmissible spongiform encephalopathies (TSE) (TSEs). The disease-causing type of a protein called cellular prion protein is this small infectious particle (PrPc). PrPc is mostly found on the surface of cells in the central nervous system, but it can also be found in other tissues of the body. Although the precise function of PrPc is unknown, studies indicate that it protects cells and aids in their response to oxygen deficiency.

A prion is composed of abnormally folded proteins that cause progressive neurodegenerative conditions, with two of the most notable being bovine spongiform encephalopathy (BSE or mad cow disease) seen in cattle and livestock and Creutzfeldt-Jakob disease (CJD) seen in humans.

These misfolded proteins do not multiply in the host organism that they infect. Instead, they affect the brain structure by acting as a template, inducing normal folding proteins to convert to abnormal prion form.

Prions are so small that they are even smaller than viruses and can only be seen by an electron microscope when they have aggregated and formed a cluster. Prions are also unique in that they do not contain nucleic acid, as opposed to bacteria, fungi, viruses and other pathogens. Prions are therefore resistant to processes that destroy pathogens by breaking down nucleic acid.

Normal prion protein is thought to consist of flexible coils referred to as alpha helices, but in an abnormally folded form, these helices are extended into densely packed structures called beta sheets. Cellular enzymes referred to as proteases may break down the normal protein, but prion proteins are resistant to this and accumulate in the brain tissue as they replicate.

Note: Proteins showing prion-type behaviour are also found in some fungi that have been useful in helping to understand mammalian prions. Fungal prions do not appear to cause disease in the hosts.