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J. Virol., 03 1996, 1714-1722, Vol 70, No. 3
D Riesner, K Kellings, K Post, H Wille, H Serban, D Groth, MA Baldwin and SB Prusiner
An abnormal isoform of the prion protein (PrP) designated PrPSc is the
major, or possibly the only, component of infectious prions. Structural
studies of PrPSc have been impeded by its lack of solubility under
conditions in which infectivity is retained. Among the many detergents
examined, only treatment with the ionic detergent sodium dodecyl sulfate
(SDS) or Sarkosyl followed by sonication dispersed prion rods which are
composed of PrP 27-30, an N-terminally truncated form of PrPSc. After
ultracentrifugation at 100,000 x g for 1 h, approximately 30% of the PrP
27-30 and scrapie infectivity were found in the supernatant, which was
fractionated by sedimentation through 5 to 20% sucrose gradients. Near the
top of the gradient, spherical particles with an observed sedimentation
coefficient of approximately 6S, approximately 10 mm in diameter and
composed of four to six PrP 27-30 molecules, were found. The spheres could
be digested with proteinase K and exhibited little, if any, scrapie
infectivity. When the prion rods were disrupted in SDS and the entire
sample was fractionated by sucrose gradient centrifugation, a lipid-rich
fraction at the meniscus composed of fragments of rods and heterogeneous
particles containing high levels of prion infectivity was found. Fractions
adjacent to the meniscus also contained spherical particles. Circular
dichroism of the spheres revealed 60% alpha-helical content; addition of
25% acetonitrile induced aggregates high in beta sheet but remaining devoid
of infectivity. Although the highly purified spherical oligomers of PrP 27-
30 lack infectivity, they may provide an excellent substrate for
determining conditions of renaturation under which prion particles regain
infectivity.
Copyright © 1996, American Society for Microbiology
Disruption of prion rods generates 10-nm spherical particles having high alpha-helical content and lacking scrapie infectivity
Institut fur Physikalische Biologie und Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine-Universitat Dusseldorf, Germany.
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