Investigation on determinants of substrate specificities of nucleotide-sugar transporters

核苷酸糖转运蛋白是非常疏水的蛋白质，长度从340 a.a.到400 a.a.不等。它们存在于高尔基体和/或内质网膜中，使它们的C端和n端暴露于细胞质中，并且极有可能具有十个跨膜螺旋。它们将细胞质中的核苷酸糖与相应的单磷酸核苷一起转运到高尔基体管腔和/或内质网管腔中。转运的核苷酸糖被糖基转移酶用作糖供体，用于合成糖蛋白的糖链。糖脂和多糖。核苷酸-糖转运基因构成了一个被HUGO基因命名委员会命名为SLC（溶质载体）35家族的基因家族。我们对基因数据库进行了数据挖掘，发现23个人类基因具有显著的相似性。根据相似性将其分为A ~ F 6个亚家族，并给出了每个基因的基因符号。我们发现hUGTrel8 （S…More LC35D2）基因与人类SLC35D1 （udp -葡萄糖醛酸/ udp - n -乙酰半乳糖胺转运蛋白）、果蝇边缘连接（frc）转运蛋白和线虫SQV-7转运蛋白的相似性约为50%，后者参与了发育和体体学过程。我们证明SLC35D2定位于高尔基体并运输udp - n -乙酰氨基葡萄糖。这些观察结果表明，SLC35D2是frc转运蛋白同源物的良好候选者。我们还从生化角度证明了一种与人类GDP聚焦转运蛋白高尔基GDP聚焦转运蛋白（Gfr）在果蝇体内特异性转运GDP聚焦蛋白，并在果蝇体内产生了Gfr的零突变体。果蝇Gfr突变体的表型被人类Gfr聚焦转运体所拯救。因此，这些零突变体是具有GDP聚焦转运体缺陷的CDGIIc患者的良好果蝇模型，可以研究患者发育缺陷的可能原因。少

Nucleotide sugar transporters are very hydrophobic proteins ranging from 340 a.a. to 400 a.a. long. They reside in Golgi apparatus and/or ER membrane exposing their C- and N-terminal regions to cytosol, and are highly likely to have ten transmembrane helices. They antiport nucleotide sugars pooled in cytosol into lumen of Golgi apparatus and/or ER lumen with the corresponding nucleoside monophosphates. The transported nucleotide sugars are utilized as sugar donors by glycosyltransferases for synthesis of sugar chains of glycoproteins. glycolipids and polysaccharides.Nucleotide-sugar transporter genes constitute a gene family that was assigned as SLC (solute carrier)35 family by the HUGO gene nomenclature committee. We carried out data mining of the gene databank, and found 23 human genes which shows significant similarity each others. We classified them into 6 subfamilies, from A to F, based on their similarity, and provided the gene symbol to each of the genes.We had found hUGTrel8 (S … More LC35D2) gene that exhibits around 50% similarity with human SLC35D1 (UDP-glucuronic acid/UDP-N-acetylgalactosamine transporter), fruitfly fringe connection (frc) transporter, and nematode SQV-7 transporter, the latter two being involved in developmental and ontological processes. We demonstrated that SLC35D2 was localized in the Golgi apparatus and transported UDP-N-acetylglucosamine. These observations indicate that SLC35D2 is a good candidate for the ortholog of frc transporter.We also biochemically demonstrated that a Drosophila homolog of the human GDP-fucose transporter, the Golgi GDP-fucose transporter (Gfr), specifically transport GDP-fucose in vitro, and generated null mutants of Gfr in Drosophila. The phenotypes of the Drosophila Gfr mutants were rescued by the human GDP-fucose transporters. Hence, these null mutants are good Drosophila models of CDGIIc patients who have defective GDP-fucose transporter to investigate the possible cause of the developmental defects in the patients. Less