Aggregation and fibrillation of bovine serum albumin
- 作者：Nikolaj K. Holm ; Stine K. Jespersen ; Lise V. Thomassen ; Tine Y. Wolff ; Pankaj Sehgal ; Line A. Thomsen ; Gunna Christiansen ; Christian Beyschau Andersen ; Anders D. Knudsen ; Daniel E. Otzen
- 关键词：Albumin ; Fibrillation ; Aggregation ; Amyloid ; Proteolysis ; Nucleation
- 刊名：Biochimica et Biophysica Acta - Proteins and Proteomics
- 出版年：2007
- 期刊代码：161_15709639
- 类别：bio
- 出版时间：September 2007
- 卷：1774
- 期：9
- 页码：1128-1138
- 文件大小：1250 K
摘要
The all-α helix multi-domain protein bovine serum albumin (BSA) aggregates at elevated temperatures. Here we show that these thermal aggregates have amyloid properties. They bind the fibril-specific dyes Thioflavin T and Congo Red, show elongated although somewhat worm-like morphology and characteristic amyloid X-ray fiber diffraction peaks. Fibrillation occurs over minutes to hours without a lag phase, is independent of seeding and shows only moderate concentration dependence, suggesting intramolecular aggregation nuclei. Nevertheless, multi-exponential increases in dye-binding signal and changes in morphology suggest the existence of different aggregate species. Although β-sheet content increases from 0 to ca. 40%upon aggregation, the aggregates retain significant amounts of α-helix structure, and lack a protease-resistant core. Thus BSA is able to form well-ordered β-sheet rich aggregates which nevertheless do not possess the same structural rigidity as classical fibrils. The aggregates do not permeabilize synthetic membranes and are not cytotoxic. The ease with which a multidomain all-α helix protein can form higher-order β-sheet structure, while retaining significant amounts of α-helix, highlights the universality of the fibrillation mechanism. However, the presence of non-β-sheet structure may influence the final fibrillar structure and could be a key component in aggregated BSA's lack of cytotoxicity.