Rajaraman K, Raman B, Ramakrishna T, Rao C M
Centre for Cellular and Molecular Biology, Hyderabad, India.
Biochem Biophys Res Commun. 1998 Aug 28;249(3):917-21. doi: 10.1006/bbrc.1998.9242.
The chaperone-like alpha-crystallin prevents aggregation of several proteins by interacting with their non-native states. Alpha-Lactalbumin adopts different non-native states under different experimental conditions. We have investigated the interaction of alpha-crystallin with three non-identical non-native states, using fluorescence, circular dichroism, and gel filtration chromatography. The compact molten globule state of apo-alpha-lactalbumin in tris buffer does not interact with alpha-crystallin. The expanded, flexible molten globule-like state of reduced apo-alpha-lactalbumin (formed at pH 7.2) also does not interact with alpha-crystallin. Only the aggregation-prone non-native state of reduced apo-alpha-lactalbumin formed at pH 6.0 interacts with alpha-crystallin to form a stable complex. The alpha-crystallin bound reduced apo-alpha-lactalbumin exhibits properties similar to those of a molten globule. Our results show that alpha-crystallin interacts only with the aggregation prone molten globule state of reduced apo-alpha-lactalbumin but not with the other non-aggregating molten globule states of the protein.
伴侣样α-晶体蛋白通过与几种蛋白质的非天然状态相互作用来防止其聚集。α-乳白蛋白在不同的实验条件下会呈现不同的非天然状态。我们利用荧光、圆二色性和凝胶过滤色谱法研究了α-晶体蛋白与三种不同的非天然状态之间的相互作用。在三羟甲基氨基甲烷缓冲液中，脱辅基α-乳白蛋白的紧密熔融球状状态不与α-晶体蛋白相互作用。还原型脱辅基α-乳白蛋白（在pH 7.2时形成）的扩展、灵活的类熔融球状状态也不与α-晶体蛋白相互作用。只有在pH 6.0时形成的易聚集的还原型脱辅基α-乳白蛋白的非天然状态与α-晶体蛋白相互作用形成稳定的复合物。与α-晶体蛋白结合的还原型脱辅基α-乳白蛋白表现出与熔融球状蛋白相似的性质。我们的结果表明，α-晶体蛋白仅与还原型脱辅基α-乳白蛋白易聚集的熔融球状状态相互作用，而不与该蛋白质的其他非聚集性熔融球状状态相互作用。
