[Nobel Prize of Medicine 1997 awarded for prion theory].

The Nobel Prize 1997 for Medicine and Physiology was awarded to S.B. Prusiner, who proposed the prion hypothesis. Prions are small 'proteinaceous infectious particles' that lack nucleic acids and hence genetic information. Prions are normal host encoded proteins but with an abnormal tertiary structure, which makes them extremely resistant to chemical and physical inactivation that would modify nucleic acids. They 'replicate' by forcing their conformation upon the normal prion proteins. Recently it was demonstrated that the prion disease, bovine spongiform encephalopathy (BSE) can be transmitted to man in whom it causes a new variant of Creutzfeldt-Jakob disease.