Departamento de Bioquímica y Biología Molecular, Universidad de Valladolid, Spain.
Biochimie. 2010 Jan;92(1):71-80. doi: 10.1016/j.biochi.2009.09.011. Epub 2009 Sep 30.
Sialic acid-binding dwarf elder agglutinin (SEA) present only in rhizomes of the medicinal plant Sambucus ebulus L., was found to be a tetrameric glycoprotein consisting of two covalently-associated dimers of an enzymic A chain with rRNA N-glycosidase activity (EC 3.2.2.22) linked to a B chain with agglutinin properties. The lectin inhibited protein synthesis by a cell-free system and depurinated ribosomes. Cloning of the corresponding gene and molecular modeling of the deduced amino acid sequence demonstrated that SEA has a three-dimensional structure which resembles that reported for other two tetrameric type 2 RIPs from Sambucus (SNAI and SSA). The lectin agglutinated red blood cells and displayed sugar affinity for sialic acid residues apart from d-galactose, binding to the mucin-producing gut goblet cells. Since sialic acid is present in animal cells, especially in epithelial lining gut cells, but not in plants, SEA could play a role in the defense against insect attack. The nucleotide sequence reported in this paper has been submitted to the GenBank nucleotide database under accession number AM981401.
唾液酸结合矮小老凝集素（SEA）仅存在于药用植物接骨木的根茎中，被发现是一种四聚体糖蛋白，由具有 RNA N-糖苷酶活性（EC 3.2.2.22）的酶 A 链的两个共价结合的二聚体与具有凝集素特性的 B 链组成。该凝集素通过无细胞系统抑制蛋白质合成并脱嘌呤核糖体。相应基因的克隆和推导的氨基酸序列的分子建模表明，SEA 具有三维结构，类似于从接骨木中报道的其他两种四聚体 2 型 RIP（SNAI 和 SSA）的结构。该凝集素凝集红细胞，并显示出除 d-半乳糖以外对唾液酸残基的糖亲和力，与产生粘蛋白的肠道杯状细胞结合。由于唾液酸存在于动物细胞中，特别是在上皮衬里的肠道细胞中，但不存在于植物中，SEA 可能在防御昆虫攻击中发挥作用。本文报道的核苷酸序列已提交给 GenBank 核苷酸数据库，登录号为 AM981401。
