Parekh R B, Tse A G, Dwek R A, Williams A F, Rademacher T W
EMBO J. 1987 May;6(5):1233-44. doi: 10.1002/j.1460-2075.1987.tb02359.x.
To examine the extent to which protein structure and tissue-type influence glycosylation, we have determined the oligosaccharide structures at each of the three glycosylation sites (Asn-23, 74 and 98) of the cell surface glycoprotein Thy-1 isolated from rat brain and thymus. The results show that there is tissue-specificity of glycosylation and that superimposed on this is a significant degree of site-specificity. On the basis of the site distribution of oligosaccharides, we find that no Thy-1 molecules are in common between the two tissues despite the amino acid sequences being identical. We suggest, therefore, that by controlling N-glycosylation a tissue creates an unique set of glycoforms (same polypeptide but with oligosaccharides that differ either in sequence or disposition). The structures at each of the three sites were also determined for the thymocyte Thy-1 that binds to lentil lectin (Thy-1 L+) and for that which does not (Thy-1 L-). Segregation of intact thymus Thy-1 into two distinct sets of glycoforms by lentil lectin was found to be due to the structures at site 74. Analysis of oligosaccharide structures at the 'passenger' sites (23 and 98) suggests that either Thy-1 L+ and Thy-1 L- molecules are made in different cell-types or that the biosynthesis of oligosaccharides at one site is influenced by the glycosylation at other sites.
为了研究蛋白质结构和组织类型对糖基化的影响程度，我们测定了从大鼠脑和胸腺中分离出的细胞表面糖蛋白Thy-1的三个糖基化位点（Asn-23、74和98）处的寡糖结构。结果表明，糖基化存在组织特异性，并且在此基础上还有显著程度的位点特异性。根据寡糖的位点分布，我们发现尽管氨基酸序列相同，但两种组织中的Thy-1分子没有共同之处。因此，我们认为通过控制N-糖基化，组织会产生一组独特的糖型（相同的多肽，但寡糖在序列或排列上不同）。还测定了与扁豆凝集素结合的胸腺细胞Thy-1（Thy-1 L+）和不与扁豆凝集素结合的胸腺细胞Thy-1（Thy-1 L-）在三个位点处的结构。发现扁豆凝集素将完整胸腺Thy-1分离成两组不同的糖型是由于74位点的结构。对“过客”位点（23和98）处寡糖结构的分析表明，要么Thy-1 L+和Thy-1 L-分子是在不同细胞类型中产生的，要么一个位点处寡糖的生物合成受其他位点糖基化的影响。
