α-水晶體蛋白為一大量存在於脊椎動物水晶體的多聚體蛋白質，並且具有分子伴護功能。囓齒動物的α-水晶體蛋白除了單體αA和αB之外，尚有一少量比例的αAins-水晶體蛋白，與αA的差別僅在αA的N端第63與64號胺基酸之間多插入了23個胺基酸。為了研究此兩蛋白質在結構與功能上的差異，我們利用大腸桿菌表現大白鼠的αA-與αAins-水晶體蛋白，並使用親和性管柱純化之。經由圓二色光譜、ANS螢光放射及活性分析，我們發現αAins-水晶體蛋白具有較多的疏水性表面，較差的熱穩定性以及較低的伴護活性；αA-水晶體蛋白的伴護活性會隨著溫度增加。在水溶液的狀態下，兩者的二級結構相似但是皆改變原有的三級結構。膠體過濾管柱層析顯示αAins-水晶體蛋白在室溫或較高溫下皆有高分子集結體，而αA僅有低分子量集結；不同比例混合的αA與αAins-水晶體蛋白在室溫下可形成分子量類似天然α-水晶體蛋白聚合體，高比例含量(超過十分之ㄧ)的αAins-水晶體蛋白會減少α-水晶體蛋白的伴護活性。

　Alpha-crystallin is a multimeric protein complex which is constitutively expressed at high level in the vertebrate eye lenses and is known to have chaperone-like activity. Apart from the major A- and B-subunit, -crystallin of rodents contains an additional minor subunit, Ains-, having an insertion peptide of 23 residues between positions 63th and 64th of normal A-crystallin. In order to explore the structural and functional consequence of the insertion peptide, we had expressed respectively rat A- and Ains-crystallins in Escherichia coli and isolated the homogeneous crystallins. We had characterized the chaperone-like activity, thermal aggregation, and the secondary and tertiary structures of the recombinant proteins, which were inserted 11 residues containing 6 histidines between 1st and 2nd residues for purification purpose. It was found that Ains-crystallin did not show no chaperone-like activity toward DTT induced insulin B aggregation. Further experiment found that Ains-crystallin could reduce the chaperone-like activity of A-crystallin when the ratio to A-crystallin was more than1:10. Thermal aggregation results showed that Ains-crystallin was capable of aggregate into high molecular weight aggregate (HMWA with MW  2000 kDa) in room or higher temperatures, whereas A-crystallin did not. We also found that Ains-crystallin was able to induce A-crystallin to form HMWA. The secondary structure of recombinant Ains- and A-crystallins were similar to the native -crystallin, however, the tertiary structure were quite different from that of -crystallin with the loss of the characteristic absorptions at 259, 265, 273, 279, and 283 nm. This study indicated that the biological purpose of Ains-crystallin in rodent animal is to induce the formation of HMWA of A-crystallin.

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