Molecular evolution of Galectins and their ligands

测定了首次发现的无脊椎动物凝集素——秀丽隐杆线虫（Caenorhabditis elegans） 32-kDa凝集基因的完整结构。只发现了两个内含子。其中一个内含子的插入位置与脊椎动物凝集素中的插入位置一致，而另一个内含子的插入位置则是独一无二的。我们还从秀丽隐杆线虫中发现了另一种与脊椎动物原型相对应的凝集素，克隆了其cDNA，并确定了其整体结构。脊椎动物和秀丽隐杆线虫都有一组相似的凝集素，这一发现强烈表明，多细胞动物中存在着不可缺少的共同生物学作用。由于基因组计划已经在秀丽隐杆线虫基因组中发现了许多半乳糖凝集素样序列（约10个），为了确认它们是否为功能基因，我们将这些序列从cDNA文库中克隆到表达载体中。一些序列被证明实际上编码了具有糖结合能力的蛋白质。有趣的是秀丽隐杆线虫和哺乳动物一样有很多凝集素。糖蛋白作为内源性半乳糖凝集素配体的候选物已经被分离出来，它们的结构特征正在被研究。免疫组化技术检测的凝集素定位也表明秀丽隐杆线虫和哺乳动物之间存在共同的生物学功能。本研究还开发了一种基于毛细管电泳的高效分析方法，用于比较不同来源的凝集素的功能。

The complete structure of the gene for 32-kDa galection of the nematode Caenorhabditis elegans, which is the firstly found invertebrate galectin, was determined. Only two introns were found. The insertion position of one intron corresponds to those found in the cases of vertebrate galectins, while that of the other was unique. We also found another galectin from C.elegans, which corresponds to the proto type of vertebrates, cloned its cDNA,and determined its whole structure. The finding that both vertebrates and C.elegans have a similar set of galectins strongly suggests the existence of common biological roles that shuould be indespensable for multicellular animals. Since many galectin-like sequences (abou 10) have been found in the genome of C.elegans as a result of the genome project, these sequences were cloned from a cDNA library into an expression vector in order to confirm whether they are functional genes or not. Some sequences were shown to actually encode proteins having sugar-binding ability. It is interesting that C.elegans has as many galectins as mammals do. Glycoproteins as possible candidates for endogenous ligands for galectins have been isolated, and their structural features are now being investigated. Localization of galectins investigated by immunohistochemical technique also indicated the existence of common biological functions between C.elegans and mammals. An efficient analytical procedure based on capillary electrophoresis for comparison of functions of galectins of different origins was also developed in this research project.