Polylactosamine glycosylation on human fetal placental fibronectin weakens the binding affinity of fibronectin to gelatin.
Polylactosamine glycosylation on human fetal placental fibronectin weakens the binding affinity of fibronectin to gelatin.
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人胎儿胎盘纤连蛋白上的聚乳糖胺糖基化削弱了纤连蛋白与明胶的结合亲和力。
DOI：
10.1016/s0021-9258(18)89228-6
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
R. Laine
中科院分区：
文献类型：
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作者：
B. C. Zhu;R. Laine
来自胎盘纤连蛋白的明胶结合胰凝乳蛋白酶片段含有聚乳糖胺碳水化合物（Zhu，B.C.R.，Fisher，S.R.，Pande，H.，Calaycay，J. Shively，J.E.，和Laine，R.A.（1984）J.Biol.Chem.259，3962-3970）。我们已经分离出含有聚乳糖胺的明胶结合片段的胎盘纤连蛋白从他们的同行含有较小的“复杂”的N-连接使用Sephadex G-200凝胶渗透色谱。两个片段的肽部分具有相似的氨基酸组成和N-末端序列（参见上文参考文献）。这两种糖基化类型的胰凝乳蛋白酶片段与明胶的结合强度不同，如以下实验所示。1)在明胶-琼脂糖色谱中亲和结合的纤连蛋白片段的尿素梯度洗脱后，含聚乳糖胺片段的洗脱峰的顶点出现在2.0 M尿素处，而含复合N-连接碳水化合物片段的峰在2.5 M尿素处最大化，表明结合更紧密。通过内切-β-半乳糖苷酶消化从前一个糖肽中去除聚乳糖胺序列导致该级分的洗脱峰从2.0 M变为2.5 M，与复杂的含N-连接碳水化合物的糖肽相同。2)竞争置换实验给出了含聚乳糖胺片段的表观解离常数为3 × 10（-9）M，而含复合碳水化合物片段的表观解离常数为1 × 10（-9）M。这些结果表明，胎盘纤连蛋白与明胶的结合被高分子量聚乳糖胺碳水化合物的存在所削弱。据我们所知，这是第一个报告，糖蛋白的糖基化的类型和程度可以影响其结合亲和力的蛋白质配体。因此，胎儿胎盘纤连蛋白可能具有与仅含有较小的N-连接复合糖的纤连蛋白不同的生物学特性。
Gelatin-binding chymotryptic fragments from placental fibronectin contain polylactosamine carbohydrates (Zhu, B.C.R., Fisher, S.R., Pande, H., Calaycay, J. Shively, J.E., and Laine, R.A. (1984) J. Biol. Chem. 259, 3962-3970). We have separated polylactosamine-containing gelatin-binding fragments of placental fibronectin from their counterparts containing smaller “complex” N-linked saccharides using Sephadex G-200 gel permeation chromatography. The peptide portions of both fragments have similar amino acid composition and N-terminal sequence (see reference above). The strength of binding of these two glycosylation types of chymotryptic fragments to gelatin differs as shown by the following experiments. 1) Upon urea gradient elution of affinity-bound fibronectin fragments from gelatin-Sepharose chromatography, the apex of the elution peak for polylactosamine-containing fragments occurs at 2.0 M urea while the peak for complex N-linked carbohydrate-containing fragments maximized at 2.5 M urea indicating a tighter binding. Removal of polylactosamine sequences from the former glycopeptide by endo-beta-galactosidase digestion caused the elution peak for this fraction to change from 2.0 to 2.5 M, the same as for the complex N-linked carbohydrate-containing glycopeptide. 2) Competitive displacement experiments give an apparent dissociation constant of polylactosamine-containing fragments at 3 X 10(-9) M whereas this constant for complex carbohydrate-containing fragments is 1 X 10(-9) M. These results indicate that the binding of placental fibronectin to gelatin is weakened by the presence of high molecular weight polylactosamine carbohydrate. To our knowledge this is the first report that the type and extent of glycosylation of a glycoprotein can affect its binding affinity to a proteinacious ligand. Thus, fetal placental fibronectin may have different biological properties than fibronectins containing only the smaller N-linked complex carbohydrate.