Bacteria, Viruses, and Protists

Virus Basics

What is a prion?

Prions are abnormal forms of natural proteins. In 1982, American neurologist and biochemist Stanley Prusiner (1942–) used the term “prion” in place of the expression “proteinaceous infectious particle” when describing an infectious agent. Scientists still have not discovered exactly how prions work. Current research shows that a prion is composed of about 250 amino acids, but no nucleic acid component has been found. They appear to accumulate in lysosomes. In the brain, it is possible that the filled lysosomes burst and damage cells. As diseased cells die, the prions contained in the cells are released and are able to attack other cells—thus, like viruses, prions are considered infectious agents. It is thought that prions are responsible for the group of brain diseases known as transmissible spongiform encephalopathies (TSEs)—including bovine spongi-form encephalopathy (mad cow disease) when it occurs in cattle and Creutzfeldt-Jakob disease when it occurs in humans.


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