Impact of the A2V Mutation on the Heterozygous and Homozygous A beta 1-40 Dimer Structures from Atomistic Simulations

The A2V mutation was reported to protect from Alzheimer’s disease in its heterozygous form and cause an early Alzheimer’s disease type dementia in its homozygous form. Experiments showed that the aggregation rate follows the order A2V > WT (wild-type) > A2V-WT. To understand the impact of this mutation, we carried out replica exchange molecular dynamics simulations of A beta 1-40 WT-A2V and A2V-A2V dimers and compared to the WT dimer. Our atomistic simulations reveal that the mean secondary structure remains constant, but there are substantial differences in the intramolecular and intermolecular conformations upon single and double A2V mutation. Upon single mutation, the intrinsic disorder is reduced, the intermolecular potential energies are reduced, the population of intramolecular three-stranded beta-sheets is increased, and the number of all a dimer topologies is decreased. Taken together, these results offer an explanation for the reduced aggregation rate of the A beta 1-40 A2V-WT peptides and the protective effect of A2V in heterozygotes.