Gitt M A, Colnot C, Poirier F, Nani K J, Barondes S H, Leffler H
Center for Neurobiology and Psychiatry, Department of Psychiatry, University of California, San Francisco, California 94143-0984, USA.
J Biol Chem. 1998 Jan 30;273(5):2954-60. doi: 10.1074/jbc.273.5.2954.
Galectins are a family of carbohydrate-binding proteins that share a conserved sequence and affinity for beta-galactosides. Some, such as galectin-1, are isolated as dimers and have a single carbohydrate recognition domain (CRD) in each monomer, whereas others, such as galectin-4, are isolated as monomers and have two CRDs in a single polypeptide chain. In the course of studying mouse colon mRNA for galectin-4, we detected a related mRNA that encodes a new galectin that also has two CRDs in a single peptide chain. The new galectin, galectin-6, lacks a 24-amino acid stretch in the link region between the two CRDs that is present in galectin-4. Otherwise, these two galectins have 83% amino acid identity. Expression of both galectin-4 and galectin-6 is confined to the epithelial cells of the embryonic and adult gastrointestinal tract. Galectin-4 is expressed at about equal levels in colon and small intestine but much less in stomach, whereas galectin-6 is expressed at about equal levels throughout the gastrointestinal tract.
半乳糖凝集素是一类碳水化合物结合蛋白家族，它们具有保守序列且对β-半乳糖苷具有亲和力。一些半乳糖凝集素，如半乳糖凝集素-1，以二聚体形式分离，每个单体中有一个单一的碳水化合物识别结构域（CRD），而其他的，如半乳糖凝集素-4，则以单体形式分离，在单一多肽链中有两个CRD。在研究小鼠结肠中半乳糖凝集素-4的mRNA过程中，我们检测到一种相关的mRNA，它编码一种新的半乳糖凝集素，该凝集素在单一肽链中也有两个CRD。新的半乳糖凝集素半乳糖凝集素-6在两个CRD之间的连接区域缺少一段24个氨基酸的片段，而这段片段存在于半乳糖凝集素-4中。除此之外，这两种半乳糖凝集素具有83%的氨基酸同一性。半乳糖凝集素-4和半乳糖凝集素-6的表达都局限于胚胎和成年胃肠道的上皮细胞。半乳糖凝集素-4在结肠和小肠中的表达水平大致相等，但在胃中的表达要少得多，而半乳糖凝集素-6在整个胃肠道中的表达水平大致相等。
