摘要：Among the various hereditary mutants of amyloid β (Aβ) in familial Alzheimer’s disease (AD), the A21G Flemish-type mutant has unique properties showing a low aggregation propensity but progressive deposition in vascular walls. Moreover, in contrast to other familial AD cases that show extensive Aβ1–42 deposition in the brain, patients with Flemish AD predominantly exhibit the deposition of the Aβ1–40 isoform. Here we report the structural characterization of the Flemish-type mutant (A21G) in comparison with the wild-type Aβ1–40 peptide to examine the possible effects of the A21G mutation on the conformation of the Aβ1–40 isoform. The kinetic analysis of the aggregation of the peptides monitored by thioflavin T fluorescence measurement indicates that the mutation precludes the initial nucleation process of amyloid fibril formation by Aβ1–40. Spectroscopic data indicate that the Flemish-type mutant bound to aqueous micelles composed of lyso-GM1, in which the mobile N-terminal segment is tethered through the C-terminal helical segment, has reduced α-helical structure compared to the wild-type peptide. Our findings suggest that the mutational perturbation to the membrane binding properties is coupled with the changes in nucleation behavior of Aβ during its fibril formation.
