Molecular chaperone-like properties of an unfolded protein, αs-casein
Molecular chaperone-like properties of an unfolded protein, αs-casein
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DOI：
10.1074/jbc.274.22.15505
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发表时间：
1999-05-28
影响因子：
4.8
通讯作者：
Das, KP
中科院分区：
文献类型：
--
作者：
Bhattacharyya, J;Das, KP
迄今为止已知的所有分子伴侣都是组织良好的折叠蛋白质分子，其三维结构被认为在底物识别和随后的折叠辅助机制中起关键作用。所有蛋白质和非蛋白质分子伴侣的共同特征是形成与胶束聚集体非常相似的聚集体的倾向。在本文中，我们表明，α（S）-酪蛋白，丰富的哺乳动物乳汁，没有明确的二级和三级结构，但存在于自然界中作为胶束聚集体，可以防止各种不相关的蛋白质/酶对热，化学，或光诱导的聚集。它还可以防止其天然底物乳清蛋白的聚集。α（s）-酪蛋白通过其溶剂暴露的疏水表面与部分未折叠的蛋白质相互作用。其序列中不存在二硫键或游离巯基在防止由巯基-二硫键交换反应引起的乳清蛋白热聚集中起重要作用。我们的研究结果表明，α（S）-酪蛋白不仅可以防止形成巨大的不溶性聚集体，但它也可以抑制积累的可溶性聚集体的可观的大小。与其他分子伴侣不同，这种蛋白质可以溶解疏水聚集的蛋白质。该蛋白具有冷休克蛋白的某些特征，其分子伴侣活性随温度的降低而增强。
All molecular chaperones known to date are well organized, folded protein molecules whose three-dimensional structure are believed to play a key role in the mechanism of substrate recognition and subsequent assistance to folding. A common feature of all protein and nonprotein molecular chaperones is the propensity to form aggregates very similar to the micellar aggregates. In this paper we show that alpha(s)-casein, abundant in mammalian milk, which has no well defined secondary and tertiary structure but exits in nature as a micellar aggregate, can prevent a variety of unrelated proteins/enzymes against thermal-, chemical-, or light-induced aggregation. It also prevents aggregation of its natural substrates, the whey proteins. alpha(s)-Casein interacts with partially unfolded proteins through its solvent-exposed hydrophobic surfaces. The absence of disulfide bridge or free thiol groups in its sequence plays important role in preventing thermal aggregation of whey proteins caused by thiol-disulfide interchange reactions. Our results indicate that alpha(s)-casein not only prevents the formation of huge insoluble aggregates but it can also inhibit accumulation of soluble aggregates of appreciable size. Unlike other molecular chaperones, this protein can solubilize hydrophobically aggregated proteins. This protein seems to have some characteristics of cold shock protein, and its chaperone-like activity increases with decrease of temperature.