[NMR paper] Amide proton solvent protection in amylin fibrils probed by quenched hydrogen exchange NMR.

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Amide proton solvent protection in amylin fibrils probed by quenched hydrogen exchange NMR.

Related Articles Amide proton solvent protection in amylin fibrils probed by quenched hydrogen exchange NMR.

PLoS One. 2013;8(2):e56467

Authors: Alexandrescu AT

Abstract
Amylin is an endocrine hormone that accumulates in amyloid plaques in patients with advanced type 2 diabetes. The amyloid plaques have been implicated in the destruction of pancreatic ?-cells, which synthesize amylin and insulin. To better characterize the secondary structure of amylin in amyloid fibrils we assigned the NMR spectrum of the unfolded state in 95% DMSO and used a quenched hydrogen-deuterium exchange technique to look at amide proton solvent protection in the fibrils. In this technique, partially exchanged fibrils are dissolved in 95% DMSO and information about amide proton occupancy in the fibrils is determined from DMSO-denatured monomers. Hydrogen exchange lifetimes at pH 7.6 and 37°C vary between ~5 h for the unstructured N-terminus to 600 h for amide protons in the two ?-strands that form inter-molecular hydrogen bonds between amylin monomers along the length of the fibril. Based on the protection data we conclude that residues A8-H18 and I26-Y37 comprise the two ?-strands in amylin fibrils. There is variation in protection within the ?-strands, particularly for strand ?1 where only residues F15-H18 are strongly protected. Differences in protection appear to be due to restrictions on backbone dynamics imposed by the packing of two-layers of C2-symmetry-related ?-hairpins in the protofilament structure, with strand ?1 positioned on the surface and ?2 in the interior.


PMID: 23457571 [PubMed - indexed for MEDLINE]



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