Molecular evolution of Galectins and their ligands

测定了线虫线虫32-kDa半乳糖凝集素基因的完整结构。线虫32-kDa半乳糖凝集素是第一个发现的无脊椎动物半乳糖凝集素。只有两个内含子被发现，其中一个内含子的插入位置与脊椎动物半乳糖凝集素的插入位置相对应，而另一个内含子的插入位置是独特的。我们还从秀丽隐杆线虫中发现了另一种半乳糖凝集素，它对应于脊椎动物的原始类型，克隆了它的cDNA，并确定了它的全结构。脊椎动物和秀丽隐杆线虫都有一组相似的半乳糖凝集素，这一发现有力地表明了多细胞动物存在着共同的生物学作用。由于基因组计划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），因此将这些序列从cDNA文库中克隆到表达载体中，以确认它们是否是功能基因。一些序列被证明实际上编码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半乳糖凝集素。作为半乳糖凝集素内源性配体的可能候选物的糖蛋白已经被分离，并且它们的结构特征现在正在被研究。免疫组化技术对半乳糖凝集素的定位研究也表明秀丽隐杆线虫与哺乳动物之间存在着共同的生物学功能。本研究还建立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半乳糖凝集素的功能。

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.