In Search of Memory: The Emergence of a New Science of Mind

by Eric R. Kandel

As Kausik looked carefully at the amino acid sequence of the novel CPEB, he noticed something very peculiar. One end of the protein had all the characteristics of a prion. Prions are probably the weirdest proteins known to modern biology. They were first discovered by Stanley Prusiner of the University of California, San Francisco as the causal agents of several mysterious neurodegenerative diseases, such as mad cow disease (bovine spongiform encephalopathy) in cattle and Creutzfeldt-Jakob disease in people (this is the disease that tragically killed Irving Kupfermann in 2002, at the prime of his scientific career). Prions differ from other proteins in that they can fold into two functionally distinct shapes, or conformations; one of these is dominant, the other recessive. The genes that encode prions give rise to the recessive form, but the recessive form can be converted to the dominant form, either by chance alone, as may have happened with Irving, or by eating food that contains an active form of the protein. In the dominant form, prions can be lethal to other cells. The second way in which prions differ from other proteins is that the dominant form is self-perpetuating; it causes the recessive conformation to change