Protein subunit

Pathology

Disease

Amyloidosis

Amyloid β

Crystallography

Biology

Gene

Biophysics

Beta-2 microglobulin

Inorganic chemistry

Chemistry

Immunology

Fibril

Amyloid (mycology)

Amyloid fibril

Protein structure

Biochemistry

Medicine

Nature Communications

All amyloid fibrils contain a cross-β fold. How this structure differs in fibrils formed from proteins associated with different diseases remains unclear. Here, we combine cryo-EM and MAS-NMR to determine the structure of an amyloid fibril formed in vitro from β 2 -microglobulin (β 2 m), the culprit protein of dialysis-related amyloidosis. The fibril is composed of two identical protofilaments assembled from subunits that do not share β 2 m’s native tertiary fold, but are formed from similar β-strands. The fibrils share motifs with other amyloid fibrils, but also contain unique features including π-stacking interactions perpendicular to the fibril axis and an intramolecular disulfide that stabilises the subunit fold. We also describe a structural model for a second fibril morphology and show that it is built from the same subunit fold. The results provide insights into the mechanisms of fibril formation and the commonalities and differences within the amyloid fold in different protein sequences.

The structure of a β2-microglobulin fibril suggests a molecular basis for its amyloid polymorphism