Amyloidogenesis is the self assembly of protein into a
fibrillar aggregate termed amyloid. Amyloid is deposited
in tissues as a consequence of certain diseases (e.g. Mad
Cow's Disease, Familial Amyloid Polyneuropathy,
Alzheimer's disease, Type II diabetes, etc. ) . The high
molecular weight and insolubility of amyloid make it
inaccessible to high resolution structural studies via
conventional methods (X-ray crystallography and solution
NMR). Electron microscopy and x-ray fiber diffraction have
provided evidence for a cross-beta structure with
beta-strands running prependicular to the long fibril
axis. We employ a combination of solid state NMR (in
collaboration with Alex Pines), hydrogen exchange, and
limited proteolysis in an effort to obtain detailed
structural information on amyloid fibrils and to
understand the mechanism of formation.
The conversion of the prion protein from it's normally
soluble predominantly a-helical form (PrPC) to an
aggregated protease reseistant form (PrPsc) high in beta
sheet content is responsible for numerous diseases (e.g.
Creutzfeld-Jakobs, Bovine Spongiform Encephalopathy).
PrPsc is infective. In vivo, Prpsc is able to convert PrPC
to PrPsc which is the basis for the protein only
hypothesis. Our efforts have focused on a model system, a
55mer mutated peptide derived from the Mouse Prion MoPrp
89-143 P101L which has been shown to be infective in
Protein Structure solved by Group Wuthrich
Preliminary solid state NMR experiments indicate that the
MoPrP 89-143 P101L peptide undergoes conformational
changes similar to the full length prion protein.
Transthyretin is a human plasma protein responsible
for the transport of retinol (complexed with retinol
binding protein). It is functional as a tetramer and is
also the primary carrier of thyroxine in the CSF.
shown in blue, RBP shown in green.
Rizzi, M. Coda, A. Science 268 (1039) 1995
TTR can be converted into amyloid fibrils in vitro by
incubating at low pH. In collaboration with Jeff Kelly's
group at TSRI, our group has shown that the native
tetramer dissociated into a monomer, and the monomer
partially unfolds before self assembling into amyloid
fibrils at low pH.