GLYCOLIPID AND GLYCOPROTEIN METABOLISM IN EYE TISSUE

与牛视紫质的寡糖链进行比较时，它们是独一无二的 对于其他糖蛋白，因为它们的大小被缩短，并且是杂交体 甘露糖含量高，类型复杂。我们正在调查使用的机制 导致这种情况的视网膜，也就是说，控制是什么 目前，半乳糖和额外的GlcNAc残基，将 未发现寡糖链扩链反应的焦点 (微量除外)成熟视紫红质。我们将延长我们的 半乳糖基转移酶动力学研究进展 这证明了视网膜酶对完整视网膜的低效率 视紫红质和视黄素。我们现在将使用低聚糖和糖肽 视紫红质制备对蛋白质基质的影响 关于这些反应。这些研究的参考化合物将是 视黄酸受体间结合蛋白(IRBP)是一种天然的 视网膜的半乳糖化糖蛋白。半乳糖基转移酶 从牛视网膜、大鼠肝脏高尔基体和牛奶中提纯的 检查过了。我们将通过免疫细胞化学来研究其定位。 半乳糖基转移酶在光感受器细胞中的表达 电子显微镜。利用分子生物学的技术，我们将 调查是否有差异的相对金额的 编码半乳糖基转移酶长型和短型的mRNAs 视网膜和感光细胞。这些是不同的亚型吗 位于光感受器细胞的不同位置；是否发现了异构体 在视网膜中主要与表面识别有关，与之相反 生物合成反应？ 将进行关于视网膜控制的调查 GlcNAc-转移酶II，一种可以将GlcNAc添加到α(1- 视紫红质低聚糖的甘露糖臂，因此是 链条延伸。这个反应的动力学，使用视紫红质，视蛋白， 视紫红质低聚糖和糖肽为受体，将 用重组DNA技术获得的酶进行检测。我们 还应检查视网膜中是否存在半乳糖苷酶和 视紫红质相关类似物的己糖氨酸酶活性。我们会 免疫亲和法分离牛光感受器细胞的尝试 层析法。人视紫质低聚糖的结构 将会被调查。 我们将继续调查关于起爆控制的问题。 在视网膜中的二羟乙醇胺途径的反应。我们将研究一下 GlcNAc-P-甘露糖对变构活化的影响 脂肪合成(我们已经发现的现象)由其他关键 该途径的中间体。 视紫红质基因突变的发现(某些位点 控制糖基化)对视网膜色素变性患者的影响 强调了了解化学和化学的重要性 视紫红质糖基化的生物化学。调查 有关多醇途径的控制可能会进一步促进我们的基本 了解糖蛋白生物合成的调控。

The oligosaccharide chains of bovine rhodopsin are unique when compared to other glycoproteins in that they are abridged in size and are hybrids of high mannose and complex types. We are investigating mechanisms used by the retina that give rise to this situation, i.e., what controls are present such that galactose and additional GlcNAc residues, that would be foci for oligosaccharide chain extension reactions, are not found (except in trace amounts) in mature rhodopsin. We shall extend our previous investigations on the kinetics of the galactosyltransferases that demonstrated the low efficiency of the retina enzyme toward intact rhodopsin and opsin. We now will use oligosaccharides and glycopeptides prepared from rhodopsin to explore the influence of the protein matrix on these reactions. A reference compound for these studies will be the interphotoreceptor retinoid binding protein (IRBP), a naturally galactosylated glycoprotein of the retina. Galactosyltransferases purified from bovine retina, from rat liver Golgi, and from milk will be examined. We shall investigate by immunocytochemistry the localization of galactosyltransferase in the photoreceptor cell using both light and electron microscopy. Using the techniques of molecular biology we shall investigate whether there are differences in the relative amounts of the mRNAs that code for the long and short forms of galactosyltransferase in the retina and the photoreceptor cell. Are these different isoforms differentially located in the photoreceptor cell; is the isoform found in the retina concerned mainly with surface recognition in contrast to biosynthetic reactions? Investigations will be carried out concerning control by the retina of GlcNAc-transferase II, an enzyme that could add a GlcNAc to the alpha(1 - > 6) mannose arm of the rhodopsin oligosaccharides and thus be a site for chain extension. The kinetics of this reaction, using rhodopsin, opsin, rhodopsin oligosaccharides and glycopeptides as acceptors, will be examined using the enzyme obtained by recombinant DNA techniques. We shall also examine for the presence in the retina of galactosidase and hexosaminidase activity toward pertinent analogs of rhodopsin. We shall attempt the isolation of bovine photoreceptor cells by immunoaffinity chromatography. The structure of the oligosaccharides of human rhodopsin will be investigated. We shall continue our investigations concerning control of the initiating reactions of the dolichol pathway in the retina. We shall examine the influence on the allosteric activation by dolichol-P-mannose of GlcNAc- lipid synthesis (a phenomenon which we have discovered) by other key intermediates of the pathway. The findings of mutations in the rhodopsin gene (some in sites controlling glycosylation) in patients with retinitis pigmentosa have highlighted the importance of understanding the chemistry and biochemistry of the glycosylation of rhodopsin. The investigations concerning control of the dolichol pathway may further our basic understanding of the regulation of glycoprotein biosynthesis.