Article

Hollow core of Alzheimer's Abeta42 amyloid observed by cryoEM is relevant at physiological pH.

Center for Cancer Research Nanobiology Program, National Cancer Institute, Frederick, MD 21702, USA.
Proceedings of the National Academy of Sciences (impact factor: 9.68). 08/2010; 107(32):14128-33. DOI:10.1073/pnas.1004704107 pp.14128-33
Source: PubMed

ABSTRACT Recent cryoEM density maps of Abeta(42) fibrils obtained at low pH revealed two protofilaments winding around a hollow core raising the question if such tubular structures also exist at physiological pH. Based on the cryoEM measurements and on NMR data, we probe amyloid fibril organizations corresponding to the observed cryoEM density map. Our study demonstrates that the tubular Abeta(42) fibril models exist at both acidic and physiological pH; however, the relative populations of the polymorphic models shift with pH. At acidic pH, the hollow core model exhibits higher population than the other models; at physiological pH, although it is less populated compared to the other models, structurally, it is stable and represents 8% of the population. We observe that only models with C termini facing the external surface of the fibril retain the hollow core under acidic and physiological conditions with dimensions similar to those observed by cryoEM; on the other hand, the hydrophobic effect shrinks the tubular cavity in the alternative organization. The existence of the hollow core fibril at physiological pH emphasizes the need to examine toxic effects of minor oligomeric species with unique organizations.

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Keywords

acidic pH
 
alternative organization
 
C termini
 
cryoEM measurements
 
hollow core
 
hollow core fibril
 
hydrophobic effect
 
low pH
 
minor oligomeric species
 
NMR data
 
observed cryoEM density map
 
physiological conditions
 
physiological pH
 
physiological pH emphasizes
 
polymorphic models shift
 
Recent cryoEM density maps
 
toxic effects
 
tubular Abeta(42)
 
tubular cavity
 
unique organizations
 

Yifat Miller