The effects of molecular crowding on the amyloid fibril formation of alpha-lactalbumin and the chaperone action of alpha-casein.
Amyloid fibrils arise from the slow aggregation of intermediately folded protein states. In this study the kinetics of the protein fibril formation of alpha-lactalbumin and its prevention by alphaS-casein in the presence and absence of the crowding agent, dextran (68 kDa), have been compared using a thioflavin T binding assay. It was found that alphaS-casein, a molecular chaperone found in bovine milk, is a potent in vitro inhibitor of alpha-lactalbumin fibrillization. The effect of alphaS-casein in preventing fibril formation was significant, although less than it is in the absence of the crowding agent, dextran. The interaction between the chaperone and the alpha-lactalbumin and structural change in the target protein are also shown using intrinsic fluorescence intensity, an ANS binding assay, CD spectroscopy and size-exclusion HPLC. In summary, alpha-casein interacts with alpha-lactalbumin and prevents amyloid formation but not as well as it does when the crowding agent, dextran, not present.
Ghahghaei
Arezou
A
Department of Biology, University of Sistan and Baluchestan, Zahedan, Iran. arezou@chem.usb.ac.ir
Divsalar
Adeleh
A
Faridi
Nasim
N
D000682:Amyloid / Q000378:metabolism; D000818:Animals; D002364:Caseins / Q000737:chemistry* / Q000378:metabolism; D002417:Cattle; D002850:Chromatography, Gel; D002942:Circular Dichroism; D003911:Dextrans / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007768:Lactalbumin / Q000737:chemistry* / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism; D017510:Protein Folding; D055503:Protein Multimerization; D013050:Spectrometry, Fluorescence; D013696:Temperature
D000682:Amyloid; D002364:Caseins; D003911:Dextrans; D018832:Molecular Chaperones; D007768:Lactalbumin