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Promotion of beta-structure by interaction of diabetes associated polypeptide (amylin) with phosphatidylcholine
L R McLean1, A Balasubramaniam
1Marion Merrell Dow Research Institute, Cincinnati, OH 45215.
Abstract:
The interaction of the diabetes associated polypeptide (amylin) with dimyristoylphosphatidylcholine (DMPC) was assessed by measurements of turbidity (absorbance at 400 nm) and secondary structure by CD spectroscopy. In trifluoroethanol, human amylin adopts a highly alpha-helical conformation while the rat peptide is less structured. In water, the rat peptide is largely disordered and the human peptide exhibits a combination of alpha- and beta-structures. Mixtures of DMPC and the rat peptide have no effect on either the turbidity of the DMPC or the CD spectrum of the peptide. By contrast, mixtures of the human peptide with DMPC form relatively clear mixtures similar to those observed with amphipathic alpha-helical peptides, but the structure adopted, based on the CD spectrum, is largely beta. These data demonstrate that fundamental differences in the structures adopted by amylins from human and rat species exist in mixtures with DMPC and suggest that these differences may be related to the formation of amyloid fibrils in the human amylin peptide which are not observed in the rat peptide.
Insights
Human amylin interacts differently with DMPC lipid bilayers compared to rat amylin, forming beta-structures. These structural differences may explain why human amylin forms amyloid fibrils, unlike rat amylin.
Area of Science:
- Biochemistry
- Molecular Biology
- Biophysics
Background:
- Amylin (diabetes-associated polypeptide) is implicated in amyloid fibril formation.
- Lipid interactions are crucial for understanding amylin's biological behavior and aggregation.
Purpose of the Study:
- To investigate the structural differences between human and rat amylin when interacting with dimyristoylphosphatidylcholine (DMPC) lipid bilayers.
- To explore how these structural differences relate to amyloid fibril formation.
Main Methods:
- Turbidity measurements (absorbance at 400 nm) to assess sample clarity and aggregation.
- Circular Dichroism (CD) spectroscopy to determine the secondary structure of amylin peptides.
- Comparative analysis of human and rat amylin in the presence of DMPC.
Main Results:
- In trifluoroethanol, human amylin is highly alpha-helical, while rat amylin is less structured.
- In water, rat amylin is disordered, and human amylin shows mixed alpha- and beta-structures.
- Human amylin forms beta-sheet structures with DMPC, leading to relatively clear mixtures.
- Rat amylin shows no significant structural changes or turbidity changes with DMPC.
Conclusions:
- Significant structural differences exist between human and rat amylin in the presence of DMPC.
- The propensity of human amylin to adopt beta-structures with DMPC may be linked to its amyloidogenic nature.
- These findings highlight species-specific interactions of amylin with lipids, relevant to diabetes and amyloidosis research.