β-Secretase (BACE1) Purification by Refolding Method and Complex with Hispidin

Alzheimer's disease (AD) is a devastating neurodegenerative disease that represents the most common form of dementia among the elderly population. The deposition of aggregated β-amyloid (Aβ) senile plaques in the human brain is a classic observation in the neuropathology of AD, yet an understanding of the mechanism of their formation remains elusive. Aβ is formed through endoproteolysis of the amyloid precursor protein (APP) by β-secretase (BACE1, β-site APP-cleaving enzyme) and γ-secretase. In this study, BACE1 protein was successfully over-expressed, purified, and refolded and utilized in a binding study with hispidin. We developed a simpler refolding method using a urea gradient and size-exclusion gel filtration to purify an active BACE1 protein variant, in larger quantities than that reported previously, and measured the binding affinity of hispidin to the BACE1 protein variant through isothermal titration calorimetry.