Keith F J, Gay N J
Department of Biochemistry, University of Cambridge, UK.
EMBO J. 1990 Dec;9(13):4299-306. doi: 10.1002/j.1460-2075.1990.tb07878.x.
The product of the Toll gene is a membrane protein required for the formation of dorso-ventral polarity during early embryogenesis in Drosophila melanogaster. It acts together with the other dorsal group gene products to specify a nuclear gradient of dorsal morphogen in the syncytial blastoderm stage embryo. Here we report the presence in Toll protein of additional sequences held in common with the human membrane receptor platelet glycoprotein 1b (Gp1b). We propose that these sequences in Toll form disulphide linked extracellular domains that are important for the binding of ligands in the perivitelline space of the embryo. In addition, we show that expression of Toll protein induced in a non-adhesive cell line promotes cellular adhesion, a property held in common with the related Drosophila glycoprotein chaoptin. Toll protein in such aggregates accumulates at sites of cell-cell interaction, a characteristic displayed by other cellular adhesion molecules. Taken together these findings suggest that the biochemical function of Toll protein is more closely analogous to that of Gp1b than previously thought.
Toll基因的产物是一种膜蛋白，在黑腹果蝇早期胚胎发生过程中，对于背腹极性的形成是必需的。它与其他背侧组基因产物共同作用，在合胞体胚盘阶段的胚胎中确定背侧形态发生素的核梯度。在此，我们报道Toll蛋白中存在与人类膜受体血小板糖蛋白1b（Gp1b）共有的其他序列。我们提出，Toll蛋白中的这些序列形成二硫键连接的细胞外结构域，这对于胚胎卵黄膜间隙中配体的结合很重要。此外，我们表明在非粘附细胞系中诱导表达的Toll蛋白可促进细胞粘附，这是与相关的果蝇糖蛋白视蛋白共有的特性。在这种聚集体中的Toll蛋白积聚在细胞间相互作用的部位，这是其他细胞粘附分子所具有的特征。综上所述，这些发现表明，Toll蛋白的生化功能比以前认为的更类似于Gp1b。
