Structure and aggregation mechanism of beta(2)-microglobulin (83-99) peptides studied by molecular dynamics simulations.

Many human neurodegenerative diseases are associated with amyloid fibril formation. The human 99-residue beta(2)-microglobulin (beta2m) is one of the most intensively studied amyloid-forming proteins. Recent studies show that the C-terminal fragments 72-99, 83-89, and 91-96 form by themselves amyloid fibrils in vitro and play a significant role in fibrillization of the full-length beta2m protein under acidic pH conditions. In this work, we have studied the equilibrium structures of the 17-residue fragment 83-99 in solution, and investigated its dimerization process by multiple molecular dynamics simulations. We find that an intertwined dimer, with the positions of the beta-strands consistent with the results for the monomer, is a possible structure for two beta2m(83-89) peptides. Based on our molecular-dynamics-generated dimeric structure, a protofibril model is proposed for the full-length beta2m protein.