Solid-Phase Synthesis and Characterization of N-Terminally Elongated A?-3-x -Peptides.

ABSTRACT: In addition to the prototypic amyloid-? (A?) peptides A?1-40 and A?1-42 , several A? variants differing in their amino and carboxy termini have been described. Synthetic availability of an A? variant is often the key to study its role under physiological or pathological conditions. Herein, we report a protocol for the efficient solid-phase peptide synthesis of the N-terminally elongated A?-peptides A?-3-38 , A?-3-40 , and A?-3-42 . Biophysical characterization by NMR spectroscopy, CD spectroscopy, an aggregation assay, and electron microscopy revealed that all three peptides were prone to aggregation into amyloid fibrils. Immunoprecipitation, followed by mass spectrometry, indicated that A?-3-38 and A?-3-40 are generated by transfected cells even in the presence of a tripartite ?-site amyloid precursor protein cleaving enzyme?1 (BACE1) inhibitor. The elongated A? peptides starting at Val(-3) can be separated from N-terminally-truncated A? forms by high-resolution isoelectric-focusing techniques, despite virtually identical isoelectric points. The synthetic A? variants and the methods presented here are providing tools to advance our understanding of the potential roles of N-terminally elongated A? variants in Alzheimer's disease.

SUBMITTER: Beyer I 

PROVIDER: S-EPMC5084751 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature