Structural heterogeneity in familial Alzheimer's disease mutants of amyloid-beta peptides

Alzheimer's disease is a neurodegenerative disorder characterized by progressive deposition of amyloid-beta (A beta) peptides in brain parenchyma and cerebral blood vessels. Several pathogenic familial mutations of A beta peptides have been identified that exhibit enhanced neurotoxicity and aggregative ability. However, knowledge of the structural characteristics of those A beta mutants is still limited. Here, we report multiple all-atom molecular dynamics simulations of the wild-type 42-residue A beta peptide (A beta 42) and its Flemish (A21G), Arctic (E22G), Dutch (E22Q), Italian (E22K), and Iowa (D23N) familial mutants in explicit water. After validating our simulations by comparison with available experimental data, we examined common/different features in the secondary and tertiary structures of the wild-type and five familial mutants of A beta 42. We found that A beta 42 peptides display quite heterogeneous secondary and tertiary structure ensembles. Such structural heterogeneity in the monomeric state would facilitate interconversions between various secondary structures during the formation of a beta-sheet-rich amyloid fibril, and may also serve as a structural basis of the amyloid polymorphism.