Structural Analysis and Aggregation Propensity of Pyroglutamate A?(3-40) in Aqueous Trifluoroethanol.

ABSTRACT: A hallmark of Alzheimer's disease (AD) is the accumulation of extracellular amyloid-? (A?) plaques in the brains of patients. N-terminally truncated pyroglutamate-modified A? (pEA?) has been described as a major compound of A? species in senile plaques. pEA? is more resistant to degradation, shows higher toxicity and has increased aggregation propensity and ?-sheet stabilization compared to non-modified A?. Here we characterized recombinant pEA?(3-40) in aqueous trifluoroethanol (TFE) solution regarding its aggregation propensity and structural changes in comparison to its non-pyroglutamate-modified variant A?(1-40). Secondary structure analysis by circular dichroism spectroscopy suggests that pEA?(3-40) shows an increased tendency to form ?-sheet-rich structures in 20% TFE containing solutions where A?(1-40) forms ?-helices. Aggregation kinetics of pEA?(3-40) in the presence of 20% TFE monitored by thioflavin-T (ThT) assay showed a typical sigmoidal aggregation in contrast to A?(1-40), which lacks ThT positive structures under the same conditions. Transmission electron microscopy confirms that pEA?(3-40) aggregated to large fibrils and high molecular weight aggregates in spite of the presence of the helix stabilizing co-solvent TFE. High resolution NMR spectroscopy of recombinantly produced and uniformly isotope labeled [U-15N]-pEA?(3-40) in TFE containing solutions indicates that the pyroglutamate formation affects significantly the N-terminal region, which in turn leads to decreased monomer stability and increased aggregation propensity.

SUBMITTER: Dammers C 

PROVIDER: S-EPMC4658145 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature