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† A. Scientists Solve a Puzzling Aspect about Prions

Narrator: This is Science Today. A prion is an infectious protein that causes disease not by the DNA or RNA of a virus or bacteria, but on the basis of their shape. One of the most puzzling aspects about prions has been if they have no genetic material, how can a single prion exist in different strains that can cause different diseases? Now, scientist Jonathan Weissman of the University of California, San Francisco has solved that puzzle by working with bakerís yeast as a model organism.

Weissman: We took precisely the same protein and misfolded it into two different shapes. And we actually did this by just changing the temperature. We misfolded it at four degrees or at thirty-seven degrees, and it misfolded into two different shapes.

Narrator: The scientists then infected the bakerís yeast with these two different shapes of the same protein Ė the result was strikingly different prion strains.

Weissman: And I think the next step is, more broadly, how often you see proteins misfolding into different conformations in much more common diseases of misfolding like Alzheimerís disease.

Narrator: For Science Today, Iím Larissa Branin.