GLYCOPROTEIN HORMONE OLIGOSACCHARIDES

糖蛋白激素促黄体激素（LH）、促卵泡激素（FSH）、促甲状腺激素 (TSH)和绒毛膜促性腺激素（CG）是一个密切相关的四个家族 二聚体蛋白质具有共同的α-亚基， 细胞特异性β亚基。LH携带Asn连接的寡糖， 以序列SO 4 -4GalNAc β 1，4GlcNAc β 1，2 Man α终止 而在同一细胞中合成的FSH含有唾液酸-Gal， SO 4-GalNAc的位置。本提案的目标是： 我们已经确定了两种转移酶的顺序作用是 负责这些硫酸化寡糖的合成， 确定这些硫酸化结构的生物功能。完成 我们将纯化磺基和GalNAc转移酶，并定义它们的结构。 动力学和底物识别参数。编码磺基- 和GalNAc转移酶将被制备和测序以建立 这些膜结合转移酶的一级结构。我们将确定 如果它们具有与其它糖基转移酶同源的区域， 高尔基体蛋白，并可能解释其特异性和定位 在高尔基体内。我们已经表明，在某些方面的肽序列， 糖蛋白激素被GalNAc-转移酶识别。氨基 将鉴定该识别标记的酸性序列。可能的 这种标记物和硫酸化结构在其他类型的 将评估糖蛋白。我们将探讨是否表达 这些转移酶受激素调节， 结构改变的寡糖的合成。功能 这些寡糖对LH和FSH分选的意义， 促性腺激素细胞内的不同颗粒，用于调节激素 将检查生物活性和用于确定从血液中的清除率。 具有相同结构的其他细胞中糖蛋白的性质 将与激素进行比较，以确定它们是否 寡糖具有相关功能。糖蛋白激素提供 一个模型系统，用于了解独特的寡糖是如何在 选择蛋白质家族。因为只有特定的成员 糖蛋白激素家族含有硫酸化寡糖，这是一种 重要的模型系统，这将使我们能够开发一个更好的 了解糖基化的生物学意义。

The glycoprotein hormones lutropin (LH), follitropin (FSH), thyrotropin (TSH), and chorionic gonadotropin (CG) are a family of four closely related dimeric proteins which share common alpha-subunits but have hormone-specific beta-subunits. LH bears Asn-linked oligosaccharides which terminate with the sequence SO4-4GalNAc beta 1,4GlcNAc beta 1, 2Man alpha whereas FSH, synthesized in the same cell, contains Sialic acid-Gal in place of SO4-GalNAc. The goals of this proposal are to characterize in depth the two transferases we have identified whose sequential action is responsible for synthesis of these sulfated oligosaccharides, and to determine the biologic function of these sulfated structures. To accomplish this we will purify the sulfo- and GalNAc-transferases, and define their kinetic and substrate recognition parameters. cDNAs coding for the sulfo- and GalNAc-transferases will be prepared and sequenced to establish the primary structures of these membrane-bound transferases. We will determine if they have regions which are homologous to other glycosyltransferases and Golgi proteins, and may account for their specificities and localization within the Golgi. We have shown that some aspect of the peptide sequence in glycoprotein hormones is recognized by the GalNAc-transferase. The amino acid sequence of this recognition marker will be identified. The possible presence of this marker and sulfated structures on other types of glycoproteins will be assessed. We will explore whether the expression of these transferases is under hormonal regulation and results in the synthesis of oligosaccharides with altered structures. The functional significance of these oligosaccharides for sorting of LH and FSH to different granules within the gonadotroph, for regulating hormone bioactivity, and for determining clearance from the blood will be examined. The properties of glycoproteins in other cells bearing the same structures will be compared with those of the hormones to determine if their oligosaccharides have related functions. The glycoprotein hormones provide a model system for understanding how unique oligosaccharides arise on select families of proteins. Since only specific members of the glycoprotein hormone family bear sulfated oligosaccharides, this is an important model system which will allow us to develop a better understanding of the biologic significance of glycosylation.