One 2015 study by US scientists found that repeated drying and wetting may render soil bound prions less infectious, although this was dependent on the soil type they were bound to. Fungi
Proteins showing prion-type behavior are also found in some fungi, which has been useful in helping to understand mammalian prions. Fungal prions do not appear to cause disease in their hosts. In yeast, protein refolding to the prion configuration is assisted by chaperone proteins such as Hsp104. All known prions induce the formation of an amyloid fold, in which the protein polymerises into an aggregate consisting of tightly packed beta sheets. Amyloid aggregates are fibrils, growing at their ends, and replicate when breakage causes two growing ends to become four growing ends. The incubation period of prion diseases is determined by the exponential growth rate associated with prion replication, which is a balance between the linear growth and the breakage of aggregates.Fungal proteins exhibiting templated conformational change were discovered in the yeast Saccharomyces cerevisiae by Reed Wickner in the early 1990s. For their mechanistic similarity to mammalian prions, they were termed yeast prions. Subsequent to this, a prion has also been found in the fungus Podospora anserina. These prions behave similarly to PrP, but, in general, are nontoxic to their hosts.
Prions are misfolded proteins that have 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. It is not known what causes a normal protein to misfold, but the resulting abnormal three-dimensional structure confers infectious properties by collapsing nearby protein molecules into the same shape. The word prion is derived from the term, "proteinaceous infectious particle". In comparison to all other known infectious agents such as viroids, viruses, bacteria, fungi, and parasites, all of which contain nucleic acids (DNA, RNA, or both), the hypothesized role of a protein as an infectious agent stands in contrast. Prion isoforms of the prion protein (PrP), whose specific function is uncertain, are hypothesized as the cause of transmissible spongiform encephalopathies (TSEs), including scrapie in sheep, chronic wasting disease (CWD) in deer, bovine spongiform encephalopathy (BSE) in cattle (commonly known as "mad cow disease") and Creutzfeldt–Jakob disease (CJD) in humans. All known prion diseases in mammals affect the structure of the brain or other neural tissue; all are progressive, have no known effective treatment, and are always fatal. Until 2015, all known mammalian prion diseases were caused by the prion protein (PrP); however, in 2015 it was hypothesized that multiple system atrophy (MSA) was caused by a prion form of alpha-synuclein.Prions are a type of intrinsically disordered protein, which change their conformation unless they are bound to a specific partner such as another protein.