Fibril structure of amyloid-β(1–42) by cryo–electron microscopy

Abstract

Amyloids are implicated in neurodegenerative diseases. Fibrillar aggregates of the amyloid-β protein (Aβ) are the main component of the senile plaques found in brains of Alzheimer's disease patients. We present the structure of an Aβ(1-42) fibril composed of two intertwined protofilaments determined by cryo-electron microscopy (cryo-EM) to 4.0-angstrom resolution, complemented by solid-state nuclear magnetic resonance experiments. The backbone of all 42 residues and nearly all side chains are well resolved in the EM density map, including the entire N terminus, which is part of the cross-β structure resulting in an overall "LS"-shaped topology of individual subunits. The dimer interface protects the hydrophobic C termini from the solvent. The characteristic staggering of the nonplanar subunits results in markedly different fibril ends, termed "groove" and "ridge," leading to different binding pathways on both fibril ends, which has implications for fibril growth.

Insights into protein misfolding and aggregation enabled by solid-state NMR spectroscopy

“…This includes negative-stain TEM, alongside unstained STEM and dark-field methods. As the evolution of cryo-EM methods continues [16–18], we can foresee exciting opportunities for the further integration of ssNMR and cryo-EM structural data, with an early example in a recent EM/ssNMR study of Aβ fibrils [17]. Another notable complementary method is EPR spectroscopy, which provides both dynamic insights and long-range structural constraints.…”

“…Although these tools traditionally have been unable to gain sub-nm resolution data, it has been especially the EM field that has made significant progress toward ever-higher resolution amyloid fibril studies (Fig. 1d) [14–17]. In the few years, it has however been especially the use of advanced solid-state NMR spectroscopy (ssNMR) that has made a lot of exciting progress in detailing atomic-level structures and structural data.…”

Electron cryomicroscopy as a powerful tool in biomedical research

“…3c). The filamentous deposits constituting the main component of senile plaques in AD, namely amyloid-β (1–42) fibrils, were also solved by cryo-EM [58]. Based on these findings, novel therapeutics might be tailored to reverse the formation of AD deposits.…”

The impact of water on the ambivalent behavior and paradoxical phenomenon of the amyloid-β fibril protein

“…Although both species sample β-rich conformers in solution that may represent prefibrillar intermediates, the probability that Aβ 42 sample these prefibrillar states is roughly an order magnitude larger than that of Aβ 40 (19). Nevertheless, it is important to note that a fibrillar structure has been determined for the Aβ 42 protein by solid-state nuclear magnetic resonance (NMR) spectroscopy, as was investigated by three research groups (20)(21)(22). The third team also studied this molecule by cryo-electron microscopy (22).…”

“…Nevertheless, it is important to note that a fibrillar structure has been determined for the Aβ 42 protein by solid-state nuclear magnetic resonance (NMR) spectroscopy, as was investigated by three research groups (20)(21)(22). The third team also studied this molecule by cryo-electron microscopy (22). On the other hand, a hairpin-like structure of the full-length Aβ 42 monomer was determined by NMR (18) and by small angle neutron scattering (23) in the presence of organic co-solvents (e.g.…”