Solid State NMR Studies Of Structural And Motional Complexity In Amyloid-Like Fibrils Of The Peptide GNNQQNY

Abstract

Solid state NMR allows the site-specific characterization of structure and dynamics in a variety of immobilized biomolecules, and thus allows a unique structural view on amyloid fibrils. These fibrils are common to various human disorders and appear to share a number of characteristic features, both in terms of their structure and formation. In the hope of delineating the biophysical details of the fibrillization process and the fibrils themselves, various groups have focused on the experimental and theoretical study of small peptide fragments of amyloid-forming proteins. One prominent system is the GNNQQNY7-13 fragment of the yeast prion protein Sup35p, since it was found to form not just amyloid-like fibrils, but also seemingly amyloid-like microcrystals. X-ray diffraction based structures from the latter have inspired numerous theoretical analyses and generalizations regarding the biophysics and structures of amyloid fibrils.We have instead applied biological solid state NMR methods to characterize the GNNQQNY fibrillar aggregates. Magic angle spinning (MAS) solid state NMR was used for various structural measurements, aimed at both the intramolecular as well as intermolecular structural motifs of the fibrils (as well as the crystalline aggregates). Our studies have revealed a remarkable complexity in these fibrils, despite the relatively small size of the peptide building blocks. This is in marked contrast with the rigid and homogeneous nature of the crystalline structures, as revealed by X-ray crystallography and solid state NMR. These observations provide further insights into the structure of the fibrils of this peptide model system and should also be of importance as input to numerous theoretical studies that rely on the crystal structure data.