Amyloid fibril formation by bovine milk κ-casein and its inhibition by the molecular chaperones αs- and β-casein
Amyloid fibril formation by bovine milk κ-casein and its inhibition by the molecular chaperones αs- and β-casein
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DOI：
10.1021/bi051352r
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发表时间：
2005-12-27
期刊：
影响因子：
2.9
通讯作者：
Carver, JA
中科院分区：
文献类型：
--
作者：
Thorn, DC;Meehan, S;Carver, JA
酪蛋白是牛奶中存在的一组独特且多样化的蛋白质。虽然酪蛋白的功能被认为主要是营养性的，但酪蛋白具有显着的稳定蛋白质的能力，即抑制蛋白质聚集和沉淀，这与小热休克蛋白 (sHsp) 家族的分子伴侣相当。此外，sHsps 已被证明可以抑制淀粉样原纤维的形成。本研究调查了 (i) 酪蛋白及其混合物、酪蛋白酸钠的原纤维形成倾向，以及 (ii) 酪蛋白在体外阻止 kappa-酪蛋白形成原纤维的能力。透射电子显微镜 (TEM) 和 X 射线纤维衍射数据表明，κ-酪蛋白在 37 摄氏度下很容易形成淀粉样原纤维，特别是在其二硫键还原后。在 37°C 下观察到的还原型和非还原型 K-酪蛋白硫代黄素 T 荧光随时间的增加被化学计量的 α(S)-和 β-酪蛋白以及疏水性染料 8-苯胺基-1-萘磺酸盐抑制；通过 TEM 验证了这些条件下 K-酪蛋白原纤维形成的抑制。我们的研究结果表明，α(S)-和β-酪蛋白是K-酪蛋白原纤维形成的有效抑制剂，并且可以防止体内大规模原纤维形成。因此，酪蛋白可能在淀粉体的形成中发挥预防作用，淀粉体是一种与乳腺组织中淀粉样沉积物积累相关的疾病。
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.