Back to Search
Start Over
Deamidation accelerates amyloid formation and alters amylin fiber structure.
- Source :
-
Journal of the American Chemical Society [J Am Chem Soc] 2012 Aug 01; Vol. 134 (30), pp. 12658-67. Date of Electronic Publication: 2012 Jul 17. - Publication Year :
- 2012
-
Abstract
- Deamidation of asparagine and glutamine is the most common nonenzymatic, post-translational modification. Deamidation can influence the structure, stability, folding, and aggregation of proteins and has been proposed to play a role in amyloid formation. However there are no structural studies of the consequences of deamidation on amyloid fibers, in large part because of the difficulty of studying these materials using conventional methods. Here we examine the effects of deamidation on the kinetics of amyloid formation by amylin, the causative agent of type 2 diabetes. We find that deamidation accelerates amyloid formation and the deamidated material is able to seed amyloid formation by unmodified amylin. Using site-specific isotope labeling and two-dimensional infrared (2D IR) spectroscopy, we show that fibers formed by samples that contain deamidated polypeptide contain reduced amounts of β-sheet. Deamidation leads to disruption of the N-terminal β-sheet between Ala-8 and Ala-13, but β-sheet is still retained near Leu-16. The C-terminal sheet is disrupted near Leu-27. Analysis of potential sites of deamidation together with structural models of amylin fibers reveals that deamidation in the N-terminal β-sheet region may be the cause for the disruption of the fiber structure at both the N- and C-terminal β-sheet. Thus, deamidation is a post-translational modification that creates fibers that have an altered structure but can still act as a template for amylin aggregation. Deamidation is very difficult to detect with standard methods used to follow amyloid formation, but isotope-labeled IR spectroscopy provides a means for monitoring sample degradation and investigating the structural consequences of deamidation.
- Subjects :
- Amides chemistry
Amyloid chemistry
Amyloid ultrastructure
Diabetes Mellitus, Type 2 metabolism
Humans
Islet Amyloid Polypeptide chemistry
Models, Molecular
Protein Processing, Post-Translational
Protein Structure, Secondary
Spectrophotometry, Infrared
Amides metabolism
Amyloid metabolism
Islet Amyloid Polypeptide metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1520-5126
- Volume :
- 134
- Issue :
- 30
- Database :
- MEDLINE
- Journal :
- Journal of the American Chemical Society
- Publication Type :
- Academic Journal
- Accession number :
- 22734583
- Full Text :
- https://doi.org/10.1021/ja3039486