Structure and Function of Animal Lectin, and Their Role in Biological Regulation.

为了阐明脊椎动物β-半乳糖苷结合凝集素的生物学意义，对鸡、小鼠和人的凝集素进行了研究。在化学结构方面，测定了两种鸡异凝素(14K型)中的一种的氨基酸全序列。因为在现有的数据库中很难找到有意义的同源序列，所以它被证明是一个独特的蛋白质。测定了ITS基因的全长序列，与氨基酸序列一致。建议在生物合成后去除引发剂蛋氨酸，并将生成的N-末端乙酰化。这一结果对凝集素向细胞外转运的机制提出了新的问题。测定了鸡16K和人胎盘凝集素的部分氨基酸序列。发现与鸡14K凝集素的某些部分有显著的同源性。这表明这些凝集素之间有很强的系统发育关系。在对人类凝集素分布的调查过程中，发现脐带血中含有较多的凝集素。纯化制剂表明，胎盘和脐带含有相同的凝集素。荧光抗体技术显示，凝集素主要分布在脐带结缔组织中。正常肝、肺组织和肿瘤组织均含有大量凝集素。制备了抗鸡14K凝集素的单抗。其中一个似乎非常有用，因为它可以识别凝集素的构象变化。关于该凝集素家族的生物活性，已发现人胎盘凝集素能刺激小鼠和人巨噬细胞产生某些肿瘤细胞杀伤因子。

In order to elucidate biological significance of vertebrate <beta> -galactoside-binding lectins, those from chicken, mouse and human were investigated. As to chemical structure, complete amino acid sequence of one of two chick isolectins (14K type) was determined. It proved to be a unique protein because it was difficult to find out significantly homologous sequence in the present data base. Complete sequence of its cDNA was also determined and it was consistent with the amino acid sequence. It was suggested that initiator methionine is removed after biosynthesis and resultant N-terminal is acetylated. The result raised a new question about the mechanism of transportation of the lectin to outside of cells. Partial amino acid sequences were determined on chicken 16K and human placenta lectins. Significant homologies to some parts of chick 14K lectin were found. This suggested strong phylogenic relation between these lectins. In the course of investigation on the distribution of the human lectin, umbilical cord was found to contain relatively large amount of the lectin. Purified preparation showed that placenta and umbilical cord contain the identical lectin. Fluorescent antibody technique showed that the lectin was distributed mainly in connective tissue of umbilical cord. Both normal and tumor tisuues of liver and lung were found to contain large amount of the lectin. Monoclonal antibodies for chick 14K lectin were prepared. One of them seemed to be very useful because it can recognize conformational change of the lectin. As to biological activity of this family of the lectins, human placenta lectin was found to be able to stimulate production of some tumor cell killing factors by mouse and human macrophages.