Aggregation kinetics in the presence of brain lipids of Aβ(1–40) cleaved from a soluble fusion protein

Abstract

The cleavage of the amyloid precursor protein by β- and γ-secretases is a key event in Alzheimer's disease. A fusion protein was constructed to investigate the cleavage rate and aggregation kinetics of amyloid-beta (1–40) (Aβ(1–40)) peptides. The peptide was expressed with a Small Ubiquitin-Like Modifier (SUMO) on the N-terminus and cleaved by a SUMO protease Ulp1. The time course of the cleavage reaction was monitored by SDS-PAGE gel with 100:1 or 1000:1 SUMO-Aβ(1–40) to Ulp1 molar ratio and in the presence of brain total lipid extract unilamellar vesicles. Similarly, the aggregation of Aβ(1–40) peptides upon cleavage was monitored by thioflavin T fluorescence assays and by circular dichroi..