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KMID : 0369820150450050407
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Jorunal of Korean Pharmaceutical Sciences
2015 Volume.45 No. 5 p.407 ~ p.413
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Investigating the chaperone activity of β-casein in preventing amyloid formation in κ-casein in the presence of dextran
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Ghahghaei Arezou
Mianeh Majid Mohammadi Dareh
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Abstract
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In vitro studies into proteins which are prone to form amyloid are very important. Today, researchers are trying to understand the exact mechanism of amyloid fibril formation because it causes many diseases. κ-Casein is a glycoprotein belonging to the family of milk phosphoprotein which plays an important role in the size, stability and performance of the casein micelles. This study investigates amyloid fibril formation by κ-casein and its prevention by β-casein in the presence and absence of crowding agent, dextran. Interaction between the chaperone and the κ-casein is investigated by thioflavin T fluorescence, intrinsic fluorescence intensity, ANS binding assay and CD spectroscopy. Fluorescence data show that dextran accelerated amyloid fibril formation of κ-casein. β-Casein acts as a molecular chaperone preventing the stress-induced amyloid formation of κ-casein. The effect of β-casein in preventing fibril formation of κ-casein in the presence of dextran was reduced, however, in the absence of dextran. This shows that dextran increases the rate of amyloid formation in κ-casein and causes some structural change in β-casein as assessed by CD spectroscopy. In summary, β-casein interacts with κ-casein and prevents amyloid formation but not as well as it does in the presence of the crowding agent, dextran.
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KEYWORD
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Amyloid, κ-Casein, β-Casein, Thioflavin T, Molecular crowding, Dextran, 1-Anilino-8-naphthalene sulfonic acid (ANS)
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