In Vitro Study of the Effect of Insulin on Amyloid β-Protein Assembly and Toxicity

Abstract

proline hydroxyls make up 21% of the hydrogen bonds between triple helices, proline hydroxyls can also be expected to contribute to the structural integrity and the mechanical properties of fibrils. Here we investigate this hypothesis by carrying out comparative molecular dynamics studies of fibrils in the presence and absence of hydroxylation. We investigate this in both rat and human type I fibrils. The structure of the human type I fibril structure is constructed using homology modeling, and its hydroxylation sites are determined using MS/MS sequencing. Expectedly, we find that in both human and rat fibrils, the presence of hydroxylation does alter the contact interface between triple-helices. Specifically, hydroxylation affects hydrogen bonding patterns, but in different ways in the two collagens, despite the two collagens sharing 94% sequence identity. However, in both rat and human fibrils, the altered local interactions have little effect on macroscopic structural properties, including D-band lengths and gapoverlap ratios. Additionally, hydroxylation only marginally increases Young's moduli, although the effects of hydroxylation are more pronounced under large (> 5%) strains. Overall, this study suggests that although local interactions between triple helices in fibrils are sensitive to hydroxylation and that there does exist some degree of plasticity in interfacial contacts between triple helices, the hallmark macroscopic properties of fibrils are not governed by hydroxylation. 2266-Plat Superresolution Imaging of Amyloid Structures over Extended Times using Transient Binding of Single Thioflavin T Molecules