A prion is a type of protein that can cause disease in animals and humans by triggering normally healthy proteins in the brain to fold abnormally. The prion mode of action is very different to bacteria and viruses as they are simply proteins, devoid of any genetic material.
Prions are misfolded proteins with the ability to transmit their misfolded shape onto normal variants of the same protein. They characterize several fatal and transmissible neurodegenerative diseases in humans and many other animals.
The term “prions” refers to abnormal, pathogenic agents that are transmissible and are able to induce abnormal folding of specific normal cellular proteins called prion proteins that are found most abundantly in the brain. The functions of these normal prion proteins are still not completely understood.
Prion diseases, also known as transmissible spongiform encephalopathies or TSEs, are a group of rare, fatal brain diseases that affect animals and humans. They are caused by an infectious agent known as a prion, which is derived from a misfolded version of a normal host protein known as prion protein.
Prions are unlike all other known disease-causing agents in that they appear to lack nucleic acid—i.e., DNA or RNA—which is the genetic material that all other organisms contain.
Prions, like all proteins, are composed of long chains of amino acids linked together. They exist in two forms. The first, PrPc, is found in abundance in nerve cells. Its exact function is unknown but it is thought to be innocuous.
Recent Advances in Understanding Mammalian Prion Structure: A Mini Review. Prions are lethal pathogens, which cause fatal neurodegenerative diseases in mammals. They are unique infectious agents and are composed of self-propagating multi-chain assemblies of misfolded host-encoded prion protein (PrP).
Magnetic particle capture of prions appears to target a general feature of PrPSc that is conserved between strains and shared among prions from different animal species, which bear different prion protein sequences.
Unlike other infectious agents, such as bacteria, viruses, and fungi, prions do not contain genetic materials such as DNA or RNA.
Scientists believe CWD proteins (prions) likely spread between animals through body fluids like feces, saliva, blood, or urine, either through direct contact or indirectly through environmental contamination of soil, food or water.
The PrP has been shown to participate in several biological processes, including neuritogenesis, neuronal homeostasis, cell signalling, cell adhesion, and a protective role against stress.
*A prion is an infectious agent composed 'misfolded' protein. *Prions are ONLY protein, NO genetic material---ALL other infectious agents contain RNA or DNA. *Prions are responsible for transmissible spongiform encephalopathies (disease within the brain) in mammals.
1. Prions act very slowly, with an incubation period of at least ten years before symptoms develop. 2. Prions are virtually indestructible; they are not destroyed or deactivated by heating to normal cooking temperature.
Low molecular weight infectious proteins
Was this answer helpful?
Prions are therefore resistant to procedures that destroy pathogens by breaking down nucleic acid. Furthermore, because these particles are an abnormal version of a normal protein that is already coded for in the body, they do not trigger a host immune response, as other pathogens do.
2 types of cells (viruses, prions and viroids are acellular – “without a cell”): 1. Prokaryotic ("before nucleus") – these guys are cells, but they have no internal membrane bound structures (no membrane-bound nucleus or membrane-bound organelles); includes only the bacteria.
Folding and Misfolding
Prions have the ability to reproduce, despite the fact that they contain no nucleic acid genome.
Prions propagate by transmitting a misfolded protein state. When a prion enters a healthy organism, it induces existing, properly folded proteins to convert into the disease-associated prion form; it acts as a template to guide the misfolding of more proteins into prion form.
"When they are healthy, they look like tiny spheres; when they are malignant, they appear as cubes" stated Giuseppe Legname, principal investigator of the Prion Biology Laboratory at the Scuola Internazionale Superiore di Studi Avanzati (SISSA) in Trieste, when describing prion proteins.
The prion protein exists in multiple conformations and its cellular isoform, PrPC, which is found in healthy organisms, is among the most extensively studied proteins. In humans, the newly synthesized and unprocessed PrPC is approximately 253 amino acids in length and has a molecular weight of 35–36 kDa (Figure 2).
The data supports the conclusion that a certain amount of infectious prion protein is present as a smaller and/or soluble form (less than approximately 15 nm in diameter).
Viroids are even more simple than viruses. They are small, circular, single-stranded molecules of infectious RNA lacking even a protein coat.
Prions are primarily found in the brain, the spinal cord and the immune system. British cows are thought to have developed the prion disease bovine spongiform encephalopathy (BSE) by eating ground-up brains, spleens and similar material.
Prions, however, are not living organisms. Prions are infectious proteins. For unknown reasons, these proteins refold abnormally and cause a domino effect in surrounding proteins which in turn mutate into stable structures. Prions will then cause tissue damage and cell death to surrounding areas.