Several neurodegenerative diseases, such as Alzheimer?s, Parkinson?s, and Huntington?s diseases, are associated with amyloid fibrils formed by different polypeptides. Recently, the atomic structure of the amyloid-forming peptide GGVVIA from the C-terminal hydrophobic segment of amyloid-β (Aβ) peptide has been determined and revealed a dry, tightly self-complementing structure between two β-sheets, termed as ?steric zipper?. In this study, several all-atom molecular dynamics simulations with explicit water were conducted to investigate the structural stability and aggregation behavior of the GGVVIA oligomers with various sizes. The results of our single-layer models suggested that the structural stability of the GGVVIA oligomers increases remarkably with increasing the numbers of β-strands. We further identified that SH2-ST2 may act as a stable seed in prompting amyloid fibril formations. Our results also demonstrated that hydrophobic interaction is the principle driving force to stabilize and associate the GGVVIA oligomers between β-strands; while the hydrophobic steric zipper formed via the side chains of V3, V4, and I5 plays a critical role in holding the two neighboring β-sheets together. Single glycine substitution at V3, V4, and I5 directly disrupted the hydrophobic steric zipper between these two β-sheets, resulting in the destabilization of the oligomers. Our simulation results provided detailed insights into understanding the aggregation behavior of the GGVVIA oligomers in the atomic level. It may also be helpful for designing new inhibitors able to prevent the fibril formation of Aβ peptide.

Key words: Neurodegenerative disease; Alzheimer?s disease; Parkinson?s disease; Huntington?s disease; Amyloid-β peptide; Steric zipper; Molecular dynamics simulation; Amyloid fibril.