title: Chaperone-like activity of beta-casein.
abstract: The caseins are major components of milk for most mammals and are secreted as large colloidal aggregates termed micelles. They have less ordered secondary and tertiary structures in comparison with typical globular proteins. In this work, beta-casein, a member of the casein family, has been demonstrated to exhibit chaperone-like activity, being able to suppress the thermal and chemical aggregation of such substrate proteins as insulin, lysozyme, alcohol dehydrogenase, and catalase by forming stable complexes with the denaturing substrate proteins. Meanwhile, beta-casein was found to not only prevent aggregation of the substrate proteins, but also solubilize the protein aggregates already formed. Data also show that beta-casein exhibits a higher chaperone-like activity than alpha-casein, likely due to the difference in the number of proline residues present and/or in the extent of exposed hydrophobic surfaces. The implications for their in vivo functions of the caseins, based on their exhibiting such in vitro chaperone-like activities, are discussed.
authors.affiliation: Department of Biological Sciences and Biotechnology, Tsinghua University, Haidian Street, Beijing 100084, China.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Zhang
authors.forename: Xinmiao
authors.initials: X
authors.lastname: Fu
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Chong
authors.initials: C
authors.lastname: Liu
authors.forename: Wangwang
authors.initials: W
authors.lastname: Jiao
authors.forename: Zengyi
authors.initials: Z
authors.lastname: Chang
mesh_terms: D000426:Alcohol Dehydrogenase / Q000737:chemistry / Q000187:drug effects; D002364:Caseins / Q000378:metabolism* / Q000494:pharmacology; D002374:Catalase / Q000737:chemistry / Q000187:drug effects; D002850:Chromatography, Gel; D004229:Dithiothreitol / Q000494:pharmacology; D006358:Hot Temperature; D007328:Insulin / Q000737:chemistry; D018832:Molecular Chaperones / Q000502:physiology*; D009113:Muramidase / Q000737:chemistry / Q000187:drug effects; D017510:Protein Folding; D020836:Protein Structure, Quaternary / Q000187:drug effects; D012995:Solubility
chemical_list: D002364:Caseins; D007328:Insulin; D018832:Molecular Chaperones; D000426:Alcohol Dehydrogenase; D002374:Catalase; D009113:Muramidase; D004229:Dithiothreitol