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

为了阐明脊椎动物半<beta>乳糖苷结合凝集素的生物学意义，对鸡、小鼠和人的脊椎动物半乳糖苷结合凝集素进行了研究。在化学结构方面，测定了两种鸡异凝集素（14 K型）之一的氨基酸序列。由于在现有的数据库中很难找到同源性很高的序列，因此它是一个独特的蛋白质。测定了其cDNA全序列，与氨基酸序列一致。有人建议，引发剂甲硫氨酸被删除后，生物合成和所得的N-末端乙酰化。这一结果对外源凝集素向细胞外转运的机制提出了新的问题。测定了鸡16 K凝集素和人胎盘凝集素的部分氨基酸序列。与鸡14 K凝集素的部分序列有较强的同源性，表明这些凝集素之间有较强的亲缘关系。在研究人凝集素分布的过程中，发现脐带中含有相对大量的凝集素。纯化后的胎盘和脐带中含有相同的凝集素。荧光抗体技术显示凝集素主要分布在脐带结缔组织中。肝、肺正常组织及肿瘤组织中均含有大量凝集素。制备了抗鸡14 K凝集素的单克隆抗体。其中一个似乎是非常有用的，因为它可以识别凝集素的构象变化。关于该家族凝集素的生物活性，发现人胎盘凝集素能够刺激小鼠和人巨噬细胞产生一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.