Berninsone P, Hirschberg C B
Department of Biochemistry and Molecular Biology, University of Massachusetts Medical Center, Worcester 01655, USA.
Ann N Y Acad Sci. 1998 Apr 15;842:91-9. doi: 10.1111/j.1749-6632.1998.tb09636.x.
The lumina of the endoplasmic reticulum and Golgi apparatus are the subcellular sites where glycosylation, sulfation, and phosphorylation of secretory and membrane-bound proteins, proteoglycans, and lipids occur. Nucleotide sugars, nucleotide sulfate, and ATP are substrates in the above reactions and must first be translocated from the cytosol into the lumen of these organelles. Translocation of these nucleotide derivatives is mediated by highly specific transporters, which are antiporters with the corresponding nucleoside monophosphate, as shown by genetic and biochemical approaches in mammals and yeast. Studies with mammalian, yeast, and protozoa mutants have shown that a defect in a specific translocator results in selective impairments of glycosylation of proteins, lipids and proteoglycans in vivo. Several of these transporters have been purified, cloned, and found to encode very hydrophobic proteins with multitransmembrane domains. Experiments with yeast and mammalian cells demonstrate that these transporters play a regulatory role in posttranslational modifications.
内质网和高尔基体的管腔是亚细胞位点，分泌性蛋白、膜结合蛋白、蛋白聚糖和脂质的糖基化、硫酸化和磷酸化在此发生。核苷酸糖、核苷酸硫酸盐和ATP是上述反应的底物，必须首先从细胞质转运到这些细胞器的管腔中。这些核苷酸衍生物的转运由高度特异性的转运蛋白介导，这些转运蛋白是与相应单磷酸核苷的反向转运体，这已通过哺乳动物和酵母中的遗传学和生物化学方法得到证实。对哺乳动物、酵母和原生动物突变体的研究表明，特定转运体的缺陷会导致体内蛋白质、脂质和蛋白聚糖糖基化的选择性损伤。其中几种转运蛋白已被纯化、克隆，并发现它们编码具有多个跨膜结构域的非常疏水的蛋白质。对酵母和哺乳动物细胞的实验表明，这些转运蛋白在翻译后修饰中起调节作用。
