Structural insights into Aβ42 oligomers using site-directed spin labeling.

Abstract

Oligomerization of the 42-residue peptide Aβ42 plays a key role in the pathogenesis of Alzheimer disease. Despite great academic and medical interest, the structures of these oligomers have not been well characterized. Site-directed spin labeling combined with electron paramagnetic resonance spectroscopy is a powerful approach for studying structurally ill-defined systems, but its application in amyloid oligomer structure study has not been systematically explored. Here we report a comprehensive structural study on a toxic Aβ42 oligomer, called globulomer, using site-directed spin labeling complemented by other techniques. Transmission electron microscopy shows that these oligomers are globular structures with diameters of ∼7-8 nm. Circular dichroism shows primarily β-structures. X-ray powder diffraction suggests a highly ordered intrasheet hydrogen-bonding network and a heterogeneous intersheet packing. Residue-level mobility analysis on spin labels introduced at 14 different positions shows a structured state and a disordered state at all labeling sites. Side chain mobility analysis suggests that structural order increases from N- to C-terminal regions. Intermolecular distance measurements at 14 residue positions suggest that C-terminal residues Gly-29-Val-40 form a tightly packed core with intermolecular distances in a narrow range of 11.5-12.5 Å. These intermolecular distances rule out the existence of fibril-like parallel in-register β-structures and strongly suggest an antiparallel β-sheet arrangement in Aβ42 globulomers.

• Authors: Lei Gu, Cong Liu, Zhefeng Guo
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 288 Issue 26 Pg. 18673-83 (Jun 28 2013) ISSN: 1083-351X [Electronic] United States
• PMID: 23687299 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Amyloid beta-Peptides
• Peptide Fragments
• Spin Labels
• Tetrazolium Salts
• Thiazoles
• amyloid beta-protein (1-42)
• thiazolyl blue

Topics

• Alzheimer Disease (metabolism)
• Amyloid beta-Peptides (chemistry)
• Animals
• Cell Survival
• Circular Dichroism
• Electron Spin Resonance Spectroscopy (methods)
• HeLa Cells
• Humans
• Microscopy, Electron, Transmission
• PC12 Cells
• Peptide Fragments (chemistry)
• Protein Folding
• Protein Structure, Secondary
• Rats
• Spin Labels
• Tetrazolium Salts
• Thiazoles
• X-Ray Diffraction