Nomura K H, Kobayashi R, Hirabayashi Y, Fujisue-Sakai M, Mizuguchi S, Nomura K
Laboratory of Developmental Biology, Department of Biology, Faculty of Science 33, Fukuoka 812, Japan.
Dev Genes Evol. 1998 Mar;208(1):9-18. doi: 10.1007/s004270050148.
Despite their wide distribution in various organisms, no physiological roles have been proposed for the human blood-group-ABO (ABH)-active trisaccharides. Here we show that monoclonal antibodies against human blood-group-B-active trisaccharides (B-substance) completely block the Ca2+-dependent cell-cell adhesion system of frog (Xenopus laevis) embryonic cells. Synthetic B-substance or B-active glycopeptides also disrupt the Ca2+ -dependent cell-cell adhesion. These results suggest that blood-group-B-active substances play a role in cell-cell adhesion. Blood-group-B-active substances were found as glycoproteins and as glycosphingolipids. In order to identify B-active glycoproteins active in cell-cell adhesion, we purified B-active membrane glycoproteins by two-dimensional electrophoresis and found that they are 45- to 58-kDa proteins with pI(s) ranging from 4.0 to 5.3. They are glycosylphosphatidyl inositol (GPI) anchored. Amino acid sequence analysis showed that the purified B-active GPI-anchored proteins are homologues of soluble Xenopus cortical granule lectins (CGL). The results suggest that the B-active membrane glycoproteins are GPI-anchored forms of the lectin and are directly involved in frog Ca 2+-dependent cell-cell adhesion.
尽管人类血型ABO（ABH）活性三糖在各种生物体中广泛分布，但尚未有人提出其生理作用。在此我们表明，针对人类血型B活性三糖（B物质）的单克隆抗体完全阻断了青蛙（非洲爪蟾）胚胎细胞的钙离子依赖性细胞间黏附系统。合成的B物质或B活性糖肽也会破坏钙离子依赖性细胞间黏附。这些结果表明，血型B活性物质在细胞间黏附中发挥作用。血型B活性物质以糖蛋白和糖鞘脂的形式被发现。为了鉴定在细胞间黏附中具有活性的B活性糖蛋白，我们通过二维电泳纯化了B活性膜糖蛋白，发现它们是分子量为45至58 kDa、等电点范围为4.0至5.3的蛋白质。它们通过糖基磷脂酰肌醇（GPI）锚定。氨基酸序列分析表明，纯化的B活性GPI锚定蛋白是可溶性非洲爪蟾皮质颗粒凝集素（CGL）的同源物。结果表明，B活性膜糖蛋白是凝集素的GPI锚定形式，直接参与青蛙的钙离子依赖性细胞间黏附。
