4 research outputs found
Fiber Diffraction of the Prion-Forming Domain HET-s(218–289) Shows Dehydration-Induced Deformation of a Complex Amyloid Structure
Amyloids
are filamentous protein aggregates that can be formed
by many different proteins and are associated with both disease and
biological functions. The pathogenicities or biological functions
of amyloids are determined by their particular molecular structures,
making accurate structural models a requirement for understanding
their biological effects. One potential factor that can affect amyloid
structures is hydration. Previous studies of simple stacked β-sheet
amyloids have suggested that dehydration does not impact structure,
but other studies indicated dehydration-related structural changes
of a putative water-filled nanotube. Our results show that dehydration
significantly affects the molecular structure of the fungal prion-forming
domain HET-s(218–289), which forms a β-solenoid with
no internal solvent-accessible regions. The dehydration-related structural
deformation of HET-s(218–289) indicates that water can play
a significant role in complex amyloid structures, even when no obvious
water-accessible cavities are present
Rapid Filament Supramolecular Chirality Reversal of HET‑s (218–289) Prion Fibrils Driven by pH Elevation
Amyloid
fibril polymorphism is not well understood despite its
potential importance for biological activity and associated toxicity.
Controlling the polymorphism of mature fibrils including their morphology
and supramolecular chirality by postfibrillation changes in the local
environment is the subject of this study. Specifically, the effect
of pH on the stability and dynamics of HET-s (218–289) prion
fibrils has been determined through the use of vibrational circular
dichroism (VCD), deep UV resonance Raman, and fluorescence spectroscopies.
It was found that a change in solution pH causes deprotonation of
Asp and Glu amino acid residues on the surface of HET-s (218–289)
prion fibrils and triggers rapid transformation of one supramolecular
chiral polymorph into another. This process involves changes in higher
order arrangements like lateral filament and fibril association and
their supramolecular chirality, while the fibril cross-β core
remains intact. This work suggests a hypothetical mechanism for HET-s
(218–289) prion fibril refolding and proposes that the interconversion
between fibril polymorphs driven by the solution environment change
is a general property of amyloid fibrils
Rapid Filament Supramolecular Chirality Reversal of HET‑s (218–289) Prion Fibrils Driven by pH Elevation
Amyloid
fibril polymorphism is not well understood despite its
potential importance for biological activity and associated toxicity.
Controlling the polymorphism of mature fibrils including their morphology
and supramolecular chirality by postfibrillation changes in the local
environment is the subject of this study. Specifically, the effect
of pH on the stability and dynamics of HET-s (218–289) prion
fibrils has been determined through the use of vibrational circular
dichroism (VCD), deep UV resonance Raman, and fluorescence spectroscopies.
It was found that a change in solution pH causes deprotonation of
Asp and Glu amino acid residues on the surface of HET-s (218–289)
prion fibrils and triggers rapid transformation of one supramolecular
chiral polymorph into another. This process involves changes in higher
order arrangements like lateral filament and fibril association and
their supramolecular chirality, while the fibril cross-β core
remains intact. This work suggests a hypothetical mechanism for HET-s
(218–289) prion fibril refolding and proposes that the interconversion
between fibril polymorphs driven by the solution environment change
is a general property of amyloid fibrils
Is Supramolecular Filament Chirality the Underlying Cause of Major Morphology Differences in Amyloid Fibrils?
The unique enhanced
sensitivity of vibrational circular dichroism
(VCD) to the formation and development of amyloid fibrils in solution
is extended to four additional fibril-forming proteins or peptides
where it is shown that the sign of the fibril VCD pattern correlates
with the sense of supramolecular filament chirality and, without exception,
to the dominant fibril morphology as observed in AFM or SEM images.
Previously for insulin, it has been demonstrated that the sign of
the VCD band pattern from filament chirality can be controlled by
adjusting the pH of the incubating solution, above pH 2 for “normal”
left-hand-helical filaments and below pH 2 for “reversed”
right-hand-helical filaments. From AFM or SEM images, left-helical
filaments form multifilament braids of left-twisted fibrils while
the right-helical filaments form parallel filament rows of fibrils
with a flat tape-like morphology, the two major classes of fibril
morphology that from deep UV resonance Raman scattering exhibit the
same cross-β-core secondary structure. Here we investigate whether
fibril supramolecular chirality is the underlying cause of the major
morphology differences in all amyloid fibrils by showing that the
morphology (twisted versus flat) of fibrils of lysozyme, apo-α-lactalbumin,
HET-s (218–289) prion, and a short polypeptide fragment of
transthyretin, TTR (105–115), directly correlates to their
supramolecular chirality as revealed by VCD. The result is strong
evidence that the chiral supramolecular organization of filaments
is the principal underlying cause of the morphological heterogeneity
of amyloid fibrils. Because fibril morphology is linked to cell toxicity,
the chirality of amyloid aggregates should be explored in the widely
used <i>in vitro</i> models of amyloid-associated diseases