Stability of a Recently Found Triple-β-Stranded Aβ1-42 Fibril Motif.

Amyloid-β peptides form polymorphous amyloid fibrils are correlated with the pathogenesis of Alzheimer's disease. Recently, a new ssNMR high-resolution structure has been reported for wild-type Aβ1-42 fibrils that is characterized by a strand-turn-strand-turn-strand motif instead of the U-shape form seen in previously known wild-type Aβ-fibril structures. Analyzing molecular dynamics simulations we comment on the relative weight of the new fibril structure and present evidence that its stability depends on hydrophobic contacts involving the C-terminal residues I41 and A42, but not on the salt bridge K28-A42. We further argue that Aβ1-42 peptides with this structure may assemble in fibrils with a 2-fold packing symmetry and discuss two possible arrangements.