Structural Studies of Amylin Fibrils Associated with Type 2 Diabetes

National Institute Of Diabetes And Digestive And Kidney Diseases

Investigators

Abstract

In the previous two fiscal years, we carried out and published experiments to determine the molecular structure of amylin fibrils with a specific morphology ("striated ribbon" morphology). This work identified the principal conformational and supramolecular structural features of the amylin fibrils, but did not lead to a unique molecular structural model. Two models were proposed, both consistent with existing data but differing in the nature of contacts between beta-sheet layers. In FY2009, we attempted additional experiments to obtain additional constraints on beta-sheet contacts. These experiments did not yield the required information. We also carried out initial solid state NMR measurements on fibrils prepared from recombinant, bacterially-expressed amylin. Unlike the synthetic amylin samples we have used previously in this project, the recombinant amylin could be prepared with uniform carbon-13 and nitrogen-15 labeling, in principle allowing multiple structural constraints to be obtained from a single fibril sample. Solid state NMR spectra of uniformly labeled, recombinant amylin (provided to us on a collaborative basis by the laboratory of A. Miranker, Yale University) are of good quality, but to date the sample quantities are too small to permit useful structural measurements. These efforts may continue in the next fiscal year.