中国水仙凝集素基因NTA的克隆、序列分析及蛋白结构预测

Cloning and Sequence Analysis of the Lectin Ortholog NTA from Chinese Narcissus(Narcissus tazetta var. Chinensis Roem) and Structure Prediction the Protein

凝集素是一种糖专一性结合蛋白,它可以识别不同的糖类。植物凝集素是植物防御系统重要的组成部分。本研究采用RT-PCR的方法,从中国水仙花蕾中克隆了凝集素基因NTA,运用生物信息学方法对其核苷酸序列、编码的氨基酸序列进行分析以及对其蛋白结构进行预测。结果表明,得到的NTA基因全长698bp,包含一个完整的开放阅读框516bp。该基因编码一个含有172个氨基酸的凝集素前体蛋白,该前体蛋白的等电点和分子量分别为5.84和18615.19Da。序列比对结果表明该基因编码的蛋白与其他单子叶植物如杂种水仙、雪花莲、君子兰、石蒜花和孤挺花的凝集素蛋白的同源性较高,分别为84%、80%、77%、78%以及82%。蛋白结构预测表明,中国水仙凝集素蛋白与洋水仙凝集素蛋白在结构上非常相似。对该基因编码的蛋白进行分析及蛋白结构模拟可知,该蛋白含有三个特殊的功能结构域和alpha-D-甘露糖结合表面(QXDXNXVXY)。

Lectins are carbohydrate-binding proteins which are important in immune responses. A full-length cDNA ofa lectin gene designated as NTA was cloned from Chinese Narcissus with the method of RT-PCR. With a size of 698 bp including an 516 bp open reading frame, the NTA encode a precursor lectin with 172 amino acids. The pI and M.W. of the protein NTA were predicted to be 5.84 and 18 615.19 Da, respectively. The homologous analysis showed that the sequence similarity between NTA and those from species as Narcissus hybrid cultivar agglutinin, Galanthus nivalis agglutinin, Clivia miniata agglutinin, L yc oris radiata agglutinin and Hip peastrum vittatum agglutinin were 84%, 80%, 77%, 78%, 82%, respectively. The prediction of the protein structure indicated that tertiary protein structure of lectin from Narcissus was similar to that of Narcissus pseudonarcissus, containing three functional domains specific for agglutination with the consensus sequence motif QXDXNXVXY involved in alpha-D-mannose recognition.