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A single disulfide bond differentiates aggregation pathways of beta2-microglobulin
Yiwen Chen1, Nikolay V Dokholyan
1Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Journal of Molecular Biology
|October 26, 2005
Summary
The disulfide bond in beta2-microglobulin (beta2m) dictates its amyloid aggregation pathway. Oxidized beta2m forms domain-swapped dimers, while reduced beta2m forms flexible filaments, impacting hemodialysis complications.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Chemistry
Background:
- Beta2-microglobulin (beta2m) amyloidosis is a complication in hemodialysis patients.
- The Cys25-Cys80 disulfide bond influences beta2m's native structure and aggregation propensity.
Purpose of the Study:
- To elucidate the molecular mechanisms differentiating oxidized and reduced beta2m aggregation.
- To compare the oligomerization pathways of beta2m under distinct redox conditions.
Main Methods:
- Molecular dynamics simulations of beta2m oligomerization.
- Analysis of protein structures under oxidized and reduced states at acidic pH.
Main Results:
- Oxidized beta2m forms domain-swapped dimers, exchanging N-terminal segments.
- Reduced beta2m forms parallel beta-sheet dimers and trimers, facilitating further aggregation.
- Both oxidized and reduced dimers are less stable than monomers, suggesting aggregation is not driven by dimer stability.
Conclusions:
- The Cys25-Cys80 disulfide bond dictates distinct beta2m aggregation pathways.
- Domain swapping drives oxidized beta2m aggregation, while parallel stacking of unfolded monomers drives reduced beta2m aggregation.
- Understanding these pathways may inform strategies to mitigate beta2m amyloidosis.