杏吧原创

PRIONS, the twisted proteins thought to cause BSE, Creutzfeldt-Jakob disease
and other related conditions need metal atoms to maintain their deadly shapes,
say researchers in London.

Prion diseases start when the shape of a brain protein called PrP changes. In
this form the protein is insoluble and begins to form clumps in the brain,
killing nerve cells. Many biologists think these misshapen proteins are the
infectious agent that spreads the disease鈥� although some think a virus is
involved.

Some prion diseases exist in several different strains. People who support
the 鈥減rotein-only鈥� theory believe that each strain represents a prion with a
slightly different shape. Now a team led by John Collinge of Imperial College,
London, has evidence that metal ions maintain the shape of the prion. 鈥淲e鈥檝e
been trying to understand this for some time,鈥� he says.

To study prion strains, researchers use an enzyme that digests protein to
break down infected brain tissue and reveal the characteristic patterns of PrP
fragments. Collinge鈥檚 team has now found that changing the amounts of copper or
zinc in a solution bathing tissue from patients with CJD seems to cause prions
to shift shape from one strain to another (Nature Cell Biology, vol 1, p 55).

If these lab-created strains of CJD could infect animals, and produce
symptoms typical of the strain in question, says Collinge, that would be the
best evidence yet for the protein-only theory.

Collinge says his lab is already working on the necessary animal experiments,
and he expects results within two years. 鈥淚f they could do that, I鈥檇 definitely
be impressed,鈥� says Laura Manuelidis of Yale University in Connecticut, a
long-standing sceptic of the protein-only theory.