Role of ATP on the interaction of α-crystallin with its substrates and its implications for the molecular chaperone function
Role of ATP on the interaction of α-crystallin with its substrates and its implications for the molecular chaperone function
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DOI：
10.1074/jbc.m404444200
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发表时间：
2004-10-08
影响因子：
4.8
通讯作者：
Das, KP
中科院分区：
文献类型：
--
作者：
Biswas, A;Das, KP
ATP在热休克蛋白大家族分子伴侣的功能中起着重要作用。然而，其在小热休克蛋白家族伴侣蛋白功能中的作用尚不清楚。本文报道了ATP在晶状体主要伴侣α -晶体蛋白的结构和功能中的作用。我们的体外研究表明，在生理温度下，ATP诱导α -晶体蛋白与底物蛋白的结合。结合过程是可逆的和低亲和性质的单位结合化学计量。4,4'-二苯胺-1,1'-二萘基-5,5-二磺酸，二钾盐的结合研究表明，ATP诱导了α -结晶蛋白上额外疏水位点的暴露，但对底物蛋白-结晶蛋白或碳酸酐酶没有明显的增强作用。平衡展开研究表明，3mm浓度的ATP对α -结晶蛋白结构的稳定作用为4.5 kJ/mol。ATP诱导的致密性使其更能抵抗胰蛋白酶裂解。atp诱导的伴侣蛋白α -结晶蛋白与底物的结合增强了其防止聚集的能力，也提高了乳酸脱氢酶从未折叠状态的再折叠率。我们的研究结果表明，所有这些效应都需要ATP与α -晶体蛋白的结合而不是其水解，因为ATP的不可水解类似物腺苷-5'- o -（3-硫代三磷酸）四锂盐代替ATP，忠实地再现了所有结果。讨论了生理温度下atp诱导的可逆蛋白-蛋白结合对体内α -晶体蛋白功能作用的影响。
ATP plays a significant role in the function of molecular chaperones of the large heat shock protein families. However, its role in the functions of chaperones of the small heat shock protein families is not understood very well. We report here a study on the role of ATP on the structure and function of the major eye lens chaperone alpha-crystallin. Our in vitro study shows that at physiological temperature, ATP induces the association of alpha-crystallin with substrate proteins. The association process is reversible and low affinity in nature with unit binding stoichiometry. 4,4'-Dianilino-1,1'-binaphthyl-5,5-disulfonic acid, dipotassium salt, binding studies show that ATP induces the exposure of additional hydrophobic sites on alpha-crystallin, but no appreciable enhancement of the same was observed for the substrate protein gamma-crystallin or carbonic anhydrase. An equilibrium unfolding study reveals that ATP at 3 mM concentration stabilizes the alpha-crystallin structure by 4.5 kJ/mol. The compactness induced by ATP makes it more resistant to tryptic cleavage. ATP-induced association of chaperone alpha-crystallin with substrate enhanced its aggregation prevention ability and also enhanced the refolding yield of lactate dehydrogenase from the unfolded state. Our results suggest that the binding of ATP to alpha-crystallin and not its hydrolysis is required for all these effects, as replacement of ATP by its nonhydrolyzable analogue adenosine-5'-O-(3-thiotriphosphate), tetralithium salt, reproduced all the results faithfully. The implication of the ATP-induced reversible protein-protein association at physiological temperatures on the functional role of alpha-crystallin in vivo is discussed.