Gene structure of serum lectins containing a collagen-like domain.

牛凝集素是一种对N-乙酰葡糖胺具有特异性的Ca^<2+>依赖性血清凝集素，是胶原凝集素的一员，每个胶原凝集素都具有胶原区和碳水化合物结合域（凝集素）。本研究通过对该蛋白的cDNA序列和基因结构的分析，揭示了其进化起源，并从基因结构上阐明了其生物学功能。1）首先，克隆了该蛋白cDNA的核心区，编码从Pro 28到Gln 203的175个氨基酸，以牛肝poly（A）^+ RNA为模板，根据已测定的部分氨基酸序列设计简并引物，通过RT-PCR方法扩增出目的基因。然后，采用巢式RACE技术扩增cDNA中的连接子的5 '端和3'端区域，将扩增的核心区、5 '端和3'端区域的cDNA片段进行亚克隆，并对插入片段进行双脱氧测序。2）以牛肝基因组DNA为模板，根据牛肝cDNA序列设计特异性引物，通过PCR方法扩增出牛肝cDNA片段。扩增的DNA片段直接测序。该基因全长7.5kb，编码区由7个外显子组成。长胶原样结构域（55个Gly-X-Y重复）是胶原蛋白的特征，由5个独立的外显子编码。颈部区域和碳水化合物识别结构域分别由单独的外显子编码。的整体外显子-内含子组织的连接蛋白是非常相似的其他collectins，如肺表面活性物质脱辅基蛋白D和甘露聚糖（甘露糖）结合蛋白，这表明这些凝集素是进化上接近，并形成了来自胶原蛋白和碳水化合物结合蛋白家族的外显子洗牌。

Bovine conglutinin is a Ca^<2+>-dependent serum lectin specific for N-acetylglucosamine and a member of the collectins, each of which possesses a collagenous region and carbohydrate binding domain (lectin) . In this study, we characterized the cDNA sequence and gene organization of conglutinin to shed light upon its evolutionary origin and and to elucidate its biological function with respect to the gene structure.1) Firstly, the core region of conglutinin cDNA,which encoded the 175 amino acids from Pro28 to Gln203, was amplified by RT-PCR with degenerate oligonucleotide primers designed from the partial amino acid sequences we had determined previously and bovine liver poly (A) ^+ RNA as a template. Then, the 5'-and 3'-end regions of the conglutinin cDNA were amplified by the nested RACE.The amplified cDNA fragments of the core, 5'-, and 3'-end region was subcloned and the inserts were sequenced by the dideoxy method. The full-length cDNA (1548bp) structure was determined.2) The conglutinin gene fragments were amplified by PCR with specific primers designed from the cDNA sequence using bovine liver genomic DNA as a template. The amplified DNA fragments were directly sequenced. The conglutinin gene spanned over 7.5kb, and the coding region of conglutinin mRNA consisted of seven exous. The long collagen-like domain (55 Gly-X-Y repeats) , which is characteristic of conglutinin, was encoded by five separate exons. The neck region and the carbohydrate-recognition domain were encoded by separate exons, respectively. The overall exon-intron organization of conglutinin was very similar to those of other collectins such as lung surfactant apoprotein D and mannan (mannose) -binding proteins, suggesting that these lectins are evolutionarily close and formed by a shuffling of exons derived from the collagen and carbohydrate-binding protein families.