Abstract
Caseins are a unique and diverse group of proteins present in bovine milk. While their function is presumed to be primarily nutritional, caseins have a remarkable ability to stabilize proteins, i.e., to inhibit protein aggregation and precipitation, that is comparable to molecular chaperones of the small heat-shock protein (sHsp) family. Additionally, sHsps have been shown to inhibit the formation of amyloid fibrils. This study investigated (i) the fibril-forming propensities of casein proteins and their mixture, sodium caseinate, and (ii) the ability of caseins to prevent in vitro fibril formation by kappa-casein. Transmission electron microscopy (TEM) and X-ray fiber diffraction data demonstrated that kappa-casein readily forms amyloid fibrils at 37 degrees C particularly following reduction of its disulfide bonds. The time-dependent increase in thioflavin T fluorescence observed for reduced and nonreduced K-casein at 37 degrees C was suppressed by stoichiometric amounts of alpha(S)- and beta-casein and by the hydrophobic dye 8-anilino-1-naphthalene sulfonate; the inhibition of K-casein fibril formation under these conditions was verified by TEM. Our findings suggest that alpha(S)- and beta-casein are potent inhibitors of K-casein fibril formation and may prevent large-scale fibril formation in vivo. Casein proteins may therefore play a preventative role in the development of corpora amylacea, a disorder associated with the accumulation of amyloid deposits in mammary tissue.
Original language | English |
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Pages (from-to) | 17027-17036 |
Number of pages | 10 |
Journal | Biochemistry |
Volume | 44 |
Issue number | 51 |
DOIs | |
Publication status | Published - 27 Dec 2005 |
Keywords / Materials (for Non-textual outputs)
- HEAT-SHOCK PROTEINS
- ALPHA-B-CRYSTALLIN
- APOLIPOPROTEIN C-II
- CORPORA-AMYLACEA
- MAMMARY-GLAND
- EXTRACELLULAR CHAPERONE
- DISULFIDE BRIDGES
- CLUSTERIN
- MECHANISM
- KINETICS