Structure of the carbohydrate units of IgA1 immunoglobulin. I. Composition, glycopeptide isolation, and structure of the asparagine-linked oligosaccharide units.
Structure of the carbohydrate units of IgA1 immunoglobulin. I. Composition, glycopeptide isolation, and structure of the asparagine-linked oligosaccharide units.
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IgA1 免疫球蛋白碳水化合物单位的结构。
DOI：
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发表时间：
1974
影响因子：
4.8
通讯作者：
S. Kornfeld
中科院分区：
文献类型：
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作者：
J. Baenziger;S. Kornfeld
摘要测定了IgA（α 1亚型）骨髓瘤蛋白的碳水化合物组成。发现仅存在于重链上的碳水化合物由每摩尔重链3摩尔唾液酸、9摩尔半乳糖、5.4摩尔甘露糖、0.8摩尔岩藻糖、8.8摩尔N-乙酰葡糖胺和5摩尔N-乙酰半乳糖胺组成。链霉蛋白酶降解蛋白质后，分离出四种主要的含糖肽组分。糖肽I由半乳糖、N-乙酰半乳糖胺、苏氨酸、丝氨酸和脯氨酸组成，摩尔比为4：5：4：5：9。发现每个N-乙酰半乳糖胺残基参与O-糖苷键，表明每条重链有5个O-糖苷键连接的寡糖单元。该糖肽的结构在以下论文中给出（Baenziger，J.，和Kornfeld，S.等人（1974）J.Biol.Chem.249，7270 - 7281。其他三种糖肽级分含有1至2个唾液酸残基、0至0.7个岩藻糖残基、2个半乳糖残基、3个甘露糖残基、4至5个N-乙酰葡糖胺残基和1个天冬酰胺残基。糖肽IIA是具有以下结构的均质糖肽：糖肽级分IIB和IIC似乎不是均质的，而是各自含有2个糖肽。在这两种情况下，其中一种糖肽可能是IIA的二唾液酸形式，含有与末端半乳糖连接的α 2，6唾液酸残基。另一个糖肽有2个而不是3个非还原性末端，来自核心甘露糖。这两个终止于唾液酸，并具有相同的序列，发现为含唾液酸的末端IIA。这些末端来自核心甘露糖的3位和6位。该糖肽的核心与IIA的核心不同之处在于具有岩藻糖残基，该岩藻糖残基最有可能与N-乙酰葡糖胺连接，该N-乙酰葡糖胺参与与肽的N-糖苷键。
Abstract The carbohydrate composition of an IgA (α1 subtype) myeloma protein has been determined. The carbohydrate, present only on the heavy chain, was found to consist of 3 moles of sialic acid, 9 mole of galactose, 5.4 moles of mannose, 0.8 moles of fucose, 8.8 moles of N-acetylglucosamine, and 5 moles of N-acetylgalactosamine per mole of heavy chain. Four major glycopeptide-containing fractions were isolated following pronase degradation of the protein. Glycopeptide I consisted of galactose, N-acetylgalactosamine, threonine, serine, and proline in the molar ratio 4:5:4:5:9. Each of the N-acetylgalactosamine residues was found to be involved in an O-glycosidic linkage, demonstrating that there are five O-glycosidically linked oligosaccharide units per heavy chain. The structure of this glycopeptide is presented in the following paper (Baenziger, J., and Kornfeld, S. (1974) J. Biol. Chem. 249, 7270–7281. The three other glycopeptide fractions contained 1 to 2 residues of sialic acid, 0 to 0.7 residue of fucose, 2 residues of galactose, 3 residues of mannose, 4 to 5 residues of N-acetylglucosamine, and 1 residue of asparagine. Glycopeptide IIA was a homogeneous glycopeptide with the following structure: Glycopeptide fractions IIB and IIC did not appear to be homogeneous, but instead each contained 2 glycopeptides. In both cases, one of the glycopeptides was probably the disialyl form of IIA containing a residue of sialic acid linked α2,6 to the terminal galactose. The other glycopeptide had 2 rather than 3 nonreducing termini arising from the core mannose. Both of these terminated in sialic acid and had the same sequence as that found for the sialic acid-containing terminus of IIA. These termini arose from positions 3 and 6 of the core mannose. The core of this glycopeptide differed from that of IIA in having a residue of fucose which was most likely linked α1,6 to the N-acetylglucosamine involved in the N-glycosidic linkage to the peptide.