Zebrafish alpha-crystallins: protein structure and chaperone-like activity compared to their mammalian orthologs.
Zebrafish alpha-crystallins: protein structure and chaperone-like activity compared to their mammalian orthologs.
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发表时间：
2005-01
期刊：
影响因子：
2.2
通讯作者：
J. Dahlman;K. Margot;L. Ding;J. Horwitz;M. Posner
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作者：
J. Dahlman;K. Margot;L. Ding;J. Horwitz;M. Posner
脊椎动物小热休克蛋白α A-和α B-晶状体蛋白有助于透镜的透明度和屈光力，并且还可以防止非天然蛋白质的聚集，否则会导致白内障。我们以前表明，斑马鱼（Danio rerio）和人类α B-晶体蛋白在一级结构和表达模式上的差异远远超过了orthopathic α A-晶体蛋白。在目前的研究中，我们进一步比较了斑马鱼和哺乳动物α-晶体蛋白的结构和功能。方法采用近紫外圆二色性光谱分析重组斑马鱼α-晶体蛋白的三级结构和热稳定性。通过测定斑马鱼和人类α-晶体蛋白在25摄氏度至40摄氏度之间的温度下防止几种靶蛋白的化学诱导聚集的能力，比较了它们的伴侣蛋白样活性。结果斑马鱼和人α A-晶状体蛋白显示出非常相似的三级结构，而α B-晶状体蛋白直系同源物显示出与斑马鱼蛋白中存在额外的芳香族氨基酸相关的差异。斑马鱼晶体蛋白的变性温度低于哺乳动物晶体蛋白。两种斑马鱼α-晶体蛋白的分子伴侣样活性是高度发散的，其中α A-晶体蛋白显示出比α B-晶体蛋白大得多的活性。结论α A晶体蛋白作为一种透镜特异性分子伴侣在斑马鱼和哺乳动物中具有相似的生理功能。斑马鱼alphaB-晶状体蛋白的伴侣样功能降低，并且缺乏晶状体外表达，表明其发挥与其哺乳动物直系同源物不同的生理作用。未来的比较研究α-晶状体蛋白从密切相关的脊椎动物物种可以帮助确定特定的结构变化，导致伴侣样活性的改变。
PURPOSE The vertebrate small heat shock proteins alphaA- and alphaB-crystallin contribute to the transparency and refractive power of the lens and may also prevent the aggregation of non-native proteins that would otherwise lead to cataracts. We previously showed that zebrafish (Danio rerio) and human alphaB-crystallin have diverged far more in primary structure and expression pattern than the orthologous alphaA-crystallins. In this current study we further compare the structure and function of zebrafish and mammalian alpha-crystallins. METHODS Near UV CD spectroscopy was used to analyze the tertiary structure and thermal stability of recombinant zebrafish alpha-crystallins. The chaperone-like activities of zebrafish and human alpha-crystallins were compared by assaying their ability to prevent the chemically induced aggregation of several target proteins at temperatures between 25 degrees C and 40 degrees C. RESULTS Zebrafish and human alphaA-crystallin showed very similar tertiary structures, while the alphaB-crystallin orthologs showed differences related to the presence of additional aromatic amino acids in the zebrafish protein. The denaturation temperatures of zebrafish crystallins were lower than those of mammals. The chaperone-like activities of the two zebrafish alpha-crystallins were highly divergent, with alphaA-crystallin showing much greater activity than alphaB-crystallin. CONCLUSIONS alphaA-crystallin serves a similar physiological function in both zebrafish and mammals as a lens specific chaperone-like molecule. The reduced chaperone-like function of zebrafish alphaB-crystallin and its lack of extralenticular expression indicates that it plays a different physiological role from its mammalian ortholog. Future comparative studies of alpha-crystallin from closely related vertebrate species can help identify specific structural changes that lead to alterations in chaperone-like activity.