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Updated: Mar 5, 2026
Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
Probing Medin Monomer Structure and its Amyloid Nucleation Using 13C-Direct Detection NMR in Combination with
Hannah A Davies1, Daniel J Rigden1, Marie M Phelan1
1Institute of Integrative Biology, University of Liverpool, Biosciences Building, Crown Street, L69 7ZB, UK.
Abstract:
Aortic medial amyloid is the most prevalent amyloid found to date, but remarkably little is known about it. It is characterised by aberrant deposition of a 5.4 kDa protein called medin within the medial layer of large arteries. Here we employ a combined approach of ab initio protein modelling and 13C-direct detection NMR to generate a model for soluble monomeric medin comprising a stable core of three β-strands and shorter more labile strands at the termini. Molecular dynamics simulations suggested that detachment of the short, C-terminal β-strand from the soluble fold exposes key amyloidogenic regions as a potential site of nucleation enabling dimerisation and subsequent fibril formation. This mechanism resembles models proposed for several other amyloidogenic proteins suggesting that despite variations in sequence and protomer structure these proteins may share a common pathway for amyloid nucleation and subsequent protofibril and fibril formation.
Insights
Aortic medial amyloid, caused by medin protein deposition, is common but poorly understood. New research models soluble medin, revealing a potential nucleation pathway for amyloid fibril formation.
Area of Science:
- Biochemistry
- Structural Biology
- Biophysics
Background:
- Aortic medial amyloid is the most prevalent form of amyloidosis.
- It involves the deposition of the medin protein in the medial layer of arteries.
- Little is currently known about the structure and formation mechanism of medin.
Purpose of the Study:
- To elucidate the structure of soluble monomeric medin.
- To investigate the molecular mechanism of medin amyloid nucleation and fibril formation.
Main Methods:
- Ab initio protein modeling was used to generate a structural model for soluble medin.
- Carbon-13 direct detection Nuclear Magnetic Resonance (NMR) spectroscopy provided experimental structural data.
- Molecular dynamics simulations were employed to study the protein's conformational changes and interactions.
Main Results:
- A stable core of three beta-strands with labile terminal strands was identified in soluble monomeric medin.
- Molecular dynamics simulations indicated that C-terminal strand detachment exposes amyloidogenic regions.
- This exposure facilitates dimerisation and subsequent fibril formation, suggesting a nucleation pathway.
Conclusions:
- The study provides a structural model for soluble medin and proposes a novel nucleation mechanism for aortic medial amyloid formation.
- This mechanism, involving the exposure of amyloidogenic regions upon conformational change, may be shared by other amyloidogenic proteins.
- Understanding this pathway is crucial for future therapeutic strategies targeting amyloid deposition in arteries.
