Ahmed H, Pohl J, Fink N E, Strobel F, Vasta G R
Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21202, USA.
J Biol Chem. 1996 Dec 20;271(51):33083-94. doi: 10.1074/jbc.271.51.33083.
The detailed characterization of a galectin from the toad (Bufo arenarum Hensel) ovary in its primary structure, carbohydrate specificity, and overall biochemical properties has provided novel information pertaining to structural and evolutionary aspects of the galectin family. The lectin consists of identical single-chain polypeptide subunits composed of 134 amino acids (calculated mass, 14,797 daltons), and its N-terminal residue, alanine, is N-acetylated. When compared to the sequences of known galectins, the B. arenarum galectin exhibited the highest identity (48% for the whole molecule and 77% for the carbohydrate recognition domain (CRD)) with the bovine spleen galectin-1, but surprisingly less identity (38% for the whole molecule and 47% for the CRD) with a galectin from Xenopus laevis skin (Marschal, P., Herrmann, J., Leffler, H., Barondes, S. H., and Cooper, D. N. W. (1992) J. Biol. Chem. 267, 12942-12949). Unlike the X. laevis galectin, the binding activity of the B. arenarum galectin for N-acetyllactosamine, the human blood group A tetrasaccharide and Galbeta1,3GalNAc relative to lactose, was in agreement with that observed for the galectin-1 subgroup and those galectins having "conserved" (type I) CRDs (Ahmed, H., and Vasta, G. R. (1994) Glycobiology 4, 545-549). Moreover, the toad galectin shares three of the six cysteine residues that are conserved in all mammalian galectins-1, but not in the galectins from X. laevis, fish, and invertebrates described so far. Based on the homologies of the B. arenarum galectin with the bovine spleen galectin-1 and X. laevis skin galectin, it should be concluded that within the galectin family the correlation between conservation of primary structure and phylogenetic distances among the source species may not be a direct one as proposed elsewhere (Hirabayashi, J., and Kasai, K. (1993) Glycobiology 3, 297-304). Furthermore, galectins with conserved (type I) CRDs, represented by the B. arenarum ovary galectin, and those with "variable" (type II) CRDs, represented by the X. laevis 16-kDa galectin, clearly constitute distinct subgroups in the extant amphibian taxa and may have diverged early in the evolution of chordate lineages.
对蟾蜍（Bufo arenarum Hensel）卵巢中的一种半乳糖凝集素在其一级结构、碳水化合物特异性和整体生化特性方面进行的详细表征，提供了与半乳糖凝集素家族的结构和进化方面相关的新信息。该凝集素由相同的单链多肽亚基组成，亚基由134个氨基酸组成（计算质量为14,797道尔顿），其N端残基丙氨酸被N - 乙酰化。与已知半乳糖凝集素的序列相比，沙蟾半乳糖凝集素与牛脾脏半乳糖凝集素 -1的同一性最高（整个分子为48%，碳水化合物识别结构域（CRD）为77%），但令人惊讶的是，与非洲爪蟾皮肤中的一种半乳糖凝集素的同一性较低（整个分子为38%，CRD为47%）（Marschal, P., Herrmann, J., Leffler, H., Barondes, S. H., and Cooper, D. N. W. (1992) J. Biol. Chem. 267, 12942 - 12949）。与非洲爪蟾半乳糖凝集素不同，沙蟾半乳糖凝集素对N - 乙酰乳糖胺、人血型A四糖和Galβ1,3GalNAc相对于乳糖的结合活性，与在半乳糖凝集素 -1亚组以及那些具有“保守”（I型）CRD的半乳糖凝集素中观察到的情况一致（Ahmed, H., and Vasta, G. R. (1994) Glycobiology 4, 545 - 549）。此外，蟾蜍半乳糖凝集素共享了所有哺乳动物半乳糖凝集素 -1中保守的六个半胱氨酸残基中的三个，但在迄今为止描述的非洲爪蟾、鱼类和无脊椎动物的半乳糖凝集素中不存在。基于沙蟾半乳糖凝集素与牛脾脏半乳糖凝集素 -1和非洲爪蟾皮肤半乳糖凝集素的同源性，应该得出结论，在半乳糖凝集素家族中，一级结构的保守性与来源物种之间的系统发育距离之间的相关性可能不像其他地方所提出的那样是直接的（Hirabayashi, J., and Kasai, K. (1993) Glycobiology 3, 297 - 304）。此外，以沙蟾卵巢半乳糖凝集素为代表的具有保守（I型）CRD的半乳糖凝集素，以及以非洲爪蟾16 kDa半乳糖凝集素为代表的具有“可变”（II型）CRD的半乳糖凝集素，在现存的两栖类分类群中显然构成了不同的亚组，并且可能在脊索动物谱系进化的早期就已经分化。
