The importance of steric zipper on the aggregation of the MVGGVV peptide derived from the amyloid β peptide

Amyloid-like fibrils are found in many fatal diseases, such as Alzheimer's disease, Parkinson's disease, type II diabetes mellitus, and prion diseases. Recently, the structural characterization of the MVGGVV peptide from the C-terminal hydrophobic segment of the amyloid-β (Aβ) peptide has revealed a general feature of amyloid-like fibrils, termed as "steric zipper", which is constituted by a tight side-chain complementation of the opposing β-sheet layers. In this study, several all-atom molecular dynamics simulations with explicit water were conducted to investigate the importance of steric zipper on the aggregation of the MVGGVV peptide. Our results show that the structural stability of the MVGGVV oligomers increases with increasing the number of β-strands. We further proposed that the octameric structure (the SH2-ST4 model in this study) is the possible nucleus seed for MVGGVV protofibril formation. Our results also demonstrated that hydrophobic interaction is the principle driving force to stabilize the adjacent β-strands while the steric zipper involved M1, V2, V5 and V6 is responsible for holding the neighboring β-sheet layers together. Finally, a twisted model of the MVGGVV assembly (SH2-ST50), based on the averaged twisted angle of ∼ 11.5° between the adjacent β-strands of the SH2-ST4 model, was proposed. Our results gain insights into the aggregation of the MVGGVV peptide in atomic details and may provide a hint for designing new inhibitors able to prevent the fibril formation of the Aβ peptide.