Effect of phosphorylation on αB-crystallin:: Differences in stability, subunit exchange and chaperone activity of homo and mixed oligomers of αB-crystallin and its phosphorylation-mimicking mutant
Effect of phosphorylation on αB-crystallin:: Differences in stability, subunit exchange and chaperone activity of homo and mixed oligomers of αB-crystallin and its phosphorylation-mimicking mutant
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DOI：
10.1016/j.jmb.2007.11.019
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发表时间：
2008-01-25
影响因子：
5.6
通讯作者：
Rao, Ch. Mohan
中科院分区：
文献类型：
--
作者：
Ahmad, Md. Falz;Raman, Bakthisaran;Rao, Ch. Mohan
磷酸化似乎是小分子热休克蛋白分子伴侣功能的调节剂之一。然而，磷酸化的作用尚未完全了解。我们已经调查了结构和功能的后果的磷酸化模拟突变的α B-晶体蛋白，一个小的热休克蛋白分子伴侣活性。我们已经使用了磷酸化模拟突变体，3D α B-晶体蛋白，其中所有三个磷酸化丝氨酸残基被替换为天冬氨酸。3D α B-晶体蛋白显示出对DTT诱导的胰岛素聚集、柠檬酸合酶热诱导的聚集和α-突触核蛋白SDS诱导的淀粉样原纤维形成的增强的分子伴侣样活性。荧光和圆二色光谱研究表明，3D α B-晶状体蛋白表现出较低的稳定性对尿素诱导的变性相比，α B-晶状体蛋白。使用荧光共振能量转移的亚基交换研究表明，与α B-晶状体蛋白相比，3D α B-晶状体蛋白表现出可观察到的亚基交换增加。由于只有部分α B-晶状体蛋白在体内被磷酸化，我们的亚基交换研究表明，未磷酸化和磷酸化亚基之间的混合寡聚体的形成可能在体内发挥作用。我们的研究表明，混合寡聚体的形成调节分子伴侣样活性。我们建议，α B-晶状体蛋白寡聚体的磷酸化程度和温度是实现小的热休克蛋白，α B-晶状体蛋白的伴侣蛋白的能力范围广泛的关键调制器。(c)2007爱思唯尔有限公司保留所有权利。
Phosphorylation appears to be one of the modulators of chaperone functions of small heat shock proteins. However, the role of phosphorylation is not completely understood. We have investigated the structural and functional consequences of a phosphorylation-mimicking mutation in alpha B-crystallin, a small heat shock protein with chaperone activity. We have used a phosphorylation-mimicking mutant, 3D alpha B-crystallin, in which all the three phosphorylatable serine residues are replaced with aspartic acid. 3D alpha B-Crystallin showed enhanced chaperone-like activity towards DTT-induced aggregation of insulin, heat-induced aggregation of citrate synthase and SDS-induced amyloid fibril formation of alpha-synuclein. Fluorescence and circular dichroism spectroscopic studies showed that 3D alpha B-crystallin exhibits lower stability towards urea-induced denaturation compared to alpha B-crystallin. Subunit exchange studies using fluorescence resonance energy transfer showed that 3D alpha B-crystallin exhibits an observable increase in subunit exchange compared to alpha B-crystallin. Since only part of alpha B-crystallin is phosphorylated in vivo, our subunit exchange studies indicate that formation of mixed oligomers between the unphosphorylated and phosphorylated subunits are likely to play a role in vivo. Our study shows that mixed-oligomer formation modulates the chaperone-like activity. We propose that the degree of phosphorylation of the alpha B-crystallin oligomers and temperature are key modulators to achieve a wide range of chaperone capabilities of the small heat shock protein, alpha B-crystallin. (c) 2007 Elsevier Ltd. All rights reserved.