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Nature 388, 228-229 (17 July 1997) |

Spongiform encephalopathies:  Tracking turncoat prion proteins

Colin L. Masters1 & Konrad Beyreuther2

The persistent fear that bovine spongiform encephalopathy (BSE, or 'mad cow' disease) has crossed species barriers into humans and other animals has increased the pressure on scientists to come up with a molecular explanation for infectivity. Two in vitro experiments, one assaying the conversion of purified mammalian prion protein (PrP) to its abnormal form in a cell-free system (reported by Raymond et al. on page 285 of this issue1) and the other investigating the polymerization of a yeast prion-like protein (described in Cellby Glover et al.2), now provide further evidence for the 'protein-only' hypothesis, in which transmission depends on the inheritance of an altered protein rather than nucleic-acid structure.