Liu Lingyun, Ghosh Joy G, Clark John I, Jiang Shaoyi
Department of Bioengineering, University of Washington, Seattle, WA 98195, USA.
Anal Biochem. 2006 Mar 15;350(2):186-95. doi: 10.1016/j.ab.2005.12.019. Epub 2006 Jan 13.
The molecular chaperone activity of alphaB crystallin, an important stress protein in humans, is regulated by physiological factors, including temperature, pH, Ca2+, and ATP. In this study, the role of these factors in regulating the subunit dynamics of human alphaB crystallin was investigated using surface plasmon resonance (SPR). SPR experiments indicate that at temperatures above 37 degrees C, where alphaB crystallin has been reported to have higher chaperone activity, the subunit dynamics of alphaB crystallin were increased with faster association and dissociation rates. SPR experiments also indicate that interactions between alphaB crystallin subunits were enhanced with much faster association and slower dissociation rates at pH values below 7.0, where alphaB crystallin has been reported to have lower chaperone activity. The results suggest that the dynamic and rapid subunit exchange rate may regulate the chaperone activity of alphaB crystallin. The effect of Ca2+ and ATP on the subunit dynamics of alphaB crystallin was minimal, suggesting that Ca2+ and ATP modulate the chaperone activity of alphaB crystallin without altering the subunit dynamics. Based on the SPR results and previously reported biochemical data for the chaperone activity of alphaB crystallin under different conditions of temperature and pH, a model for the relationship between the subunit dynamics and chaperone activity of alphaB crystallin is established. The model is consistent with previous biochemical data for the chaperone activity and subunit dynamics of small heat shock proteins (sHSPs) and establishes a working hypothesis for the relationship between complex assembly and chaperone activity for sHSPs.
αB晶状体蛋白是人类一种重要的应激蛋白，其分子伴侣活性受温度、pH值、Ca2+和ATP等生理因素调控。在本研究中，利用表面等离子体共振（SPR）研究了这些因素在调节人αB晶状体蛋白亚基动力学中的作用。SPR实验表明，在高于37摄氏度的温度下（据报道αB晶状体蛋白在此温度下具有更高的分子伴侣活性），αB晶状体蛋白的亚基动力学增强，结合和解离速率加快。SPR实验还表明，在pH值低于7.0时（据报道αB晶状体蛋白在此pH值下分子伴侣活性较低），αB晶状体蛋白亚基之间的相互作用增强，结合速率更快，解离速率更慢。结果表明，动态且快速的亚基交换速率可能调节αB晶状体蛋白的分子伴侣活性。Ca2+和ATP对αB晶状体蛋白亚基动力学的影响最小，这表明Ca2+和ATP在不改变亚基动力学的情况下调节αB晶状体蛋白的分子伴侣活性。基于SPR结果以及先前报道的αB晶状体蛋白在不同温度和pH条件下分子伴侣活性的生化数据，建立了αB晶状体蛋白亚基动力学与分子伴侣活性之间关系的模型。该模型与先前关于小分子热休克蛋白（sHSPs）分子伴侣活性和亚基动力学的生化数据一致，并为sHSPs的复合物组装与分子伴侣活性之间的关系建立了一个工作假设。
