The macromolecular properties of blood-group-specific glycoproteins. Characterization of a series of fractions obtained by density-gradient ultracentrifugation.
The macromolecular properties of blood-group-specific glycoproteins. Characterization of a series of fractions obtained by density-gradient ultracentrifugation.
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血型特异性糖蛋白的大分子特性。
DOI：
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发表时间：
1974
影响因子：
4.1
通讯作者：
J. Michael Creeth
中科院分区：
文献类型：
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作者：
K. Ramakrishnan Bhaskar;J. Michael Creeth
1. 平衡密度梯度超离心在铯盐中被用于从人卵巢囊肿液中分离和分离糖蛋白组分。由此得到的八个主要亚组分是详细的物理化学表征的主题。2. 分数在浮力-密度分布上呈单峰分布，但rho(0)值在1.31 ~ 1.35之间具有离散性。3. 重量-平均分子量和沉降系数随馏分密度的减小而有规律地减小，而部分比容和选择性溶剂化参数则增大。后一种行为与较轻馏分中肽含量的增加密切相关。4. 虽然所有的组分都在先前观察到的Le(a)特异性血型物质的范围内，但它们的分析组成范围很广。所有馏分的Le(a)活性大致相等。肽含量从密度最大的7%到最轻的15%不等，但氨基酸的相对分布在整个系列中基本保持不变。其中，丝氨酸+苏氨酸+脯氨酸约占各组分肽含量的50%。半乳糖和n -乙酰氨基葡萄糖含量随多肽含量的增加而降低，而n -乙酰半乳糖和唾液酸含量则相反。n -乙酰半乳糖胺与丝氨酸和苏氨酸的摩尔比基本保持在0.8-0.9，表明所有分子的糖基化程度都很高，但n -乙酰氨基葡萄糖与n -乙酰半乳糖胺的摩尔比随着肽含量的增加而稳步下降，表明存在不同长度的低聚糖侧链。根据公认的糖蛋白分子结构对结果进行了讨论。5. 用苯酚从同一囊液中提取的糖蛋白的实验证实，在铯盐中平衡离心不会去除任何非共价结合蛋白，也不会导致这些糖蛋白分子的三级结构发生任何变化。
1. Equilibrium density-gradient ultracentrifugation in caesium salts was used in two stages in the isolation and subfractionation of the glycoprotein component from a human ovarian-cyst fluid. The eight main subfractions thus obtained were the subject of detailed physicochemical characterization. 2. The fractions were unimodal in buoyant-density distribution, but had discrete rho(0) values ranging from 1.31 to 1.35. 3. Weight-average molecular weights and sedimentation coefficients decreased regularly with decreasing density of the fraction, whereas the partial specific volumes and selective solvation parameters increased. The latter behaviour correlates well with the increasing peptide content of the lighter fractions. 4. The fractions exhibited a range of analytical composition, although all were within the limits previously observed for blood-group substances of Le(a) specificity. All fractions had approximately equal Le(a) activity. The peptide content varied systematically from 7% for the densest fraction to 15% for the lightest, but the relative distributions of the amino acids remained essentially constant throughout the series. In particular, serine plus threonine plus proline made up about 50% of the peptide content of all the fractions. Fucose, galactose and N-acetylglucosamine contents decreased with increasing peptide content of the fractions, but N-acetylgalactosamine and sialic acid exhibited the opposite trend. Molar ratios of N-acetylgalactosamine to the sum of serine and threonine remained essentially constant at 0.8-0.9, implying a high degree of glycosylation of all the molecules, but the ratio of N-acetylglucosamine to N-acetylgalactosamine decreased steadily with increasing peptide content, suggesting the presence of oligosaccharide side chains of various lengths. The results are discussed in terms of the accepted structure of glycoprotein molecules. 5. Experiments on the glycoproteins extracted with phenol from the same cyst fluid have confirmed that equilibrium centrifugation in caesium salts does not remove any non-covalently bound protein nor cause any changes in the tertiary structures of these glycoprotein molecules.