Purification and structural characterization of a filamentous, mucin-like proteophosphoglycan secreted by Leishmania parasites
Purification and structural characterization of a filamentous, mucin-like proteophosphoglycan secreted by Leishmania parasites
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DOI：
10.1074/jbc.271.35.21583
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发表时间：
1996-08-30
影响因子：
4.8
通讯作者：
Bacic, A
中科院分区：
文献类型：
--
作者：
Ilg, T;Stierhof, YD;Bacic, A
利什曼原虫属的寄生原生动物分泌一种形成网络的丝状大分子，似乎与细胞聚集有关。我们在这里报告的纯化，这种寄生虫抗原从利什曼原虫培养上清液和其组成（75.6%的碳水化合物，20%的磷酸盐，4.4%的氨基酸，w/w），结构和超微结构表征为一个非常不寻常的蛋白磷酸聚糖（PPG）。优先裂解己糖1-磷酸键的温和酸水解释放PPG聚糖。它们的结构是Gal beta 1 - 4Man、Man alpha 1 - 2Man、Gal beta 1 - 3Gal beta 1 - 4Man、PO 4 - 6（Gal beta 1 - 3）（0 - 2）Gal beta 1 - 4Man和PO 4 - 6（Ara beta 1 - 2Gal beta 1 - 3）Gal beta 1 - 4Man。这些聚糖也是寄生虫糖脂脂磷酸聚糖的组分，但它们在PPG中的相对丰度和结构组织不同。它们中的一些代表了蛋白质糖基化的新形式。天然PPG上的P-31 NMR证明磷酸盐仅存在于磷酸二酯键中，并且基本结构R-Man α 1-PO 4 - 6-Gal-R连接聚糖。与磷酸丝氨酸（最可能是R-Man α 1-PO4-Ser）的磷酸二酯键将PPG寡糖锚定在多肽上。PPG具有独特的氨基酸组成;糖基化磷酸丝氨酸（> 43 mol %）、丝氨酸、丙氨酸和脯氨酸占87 mol %以上，并且似乎聚集在大的蛋白酶抗性结构域中。纯化的PPG的电子显微镜显示电缆样，灵活的，长（至6 μ m），和无分支的细丝。PPG的整体结构显示出与哺乳动物粘蛋白的许多相似性。这种新的粘蛋白样分子的寄生虫的潜在功能进行了讨论。
Parasitic protozoa of the genus Leishmania secrete a filamentous macromolecule that forms networks and appears to be associated with cell aggregation. We report here the purification of this parasite antigen from Leishmania major culture supernatant and its compositional (75.6% carbohydrate, 20% phosphate, 4.4% amino acids, w/w), structural, and ultrastructural characterization as a highly unusual proteophosphoglycan (PPG). Mild acid hydrolysis, which cleaves preferentially hexose 1-phosphate bonds, releases the PPG glycans. Their structures are Gal beta 1-4Man, Man alpha 1-2Man, Gal beta 1-3Gal beta 1-4Man, PO4-6(Gal beta 1-3)(0-2)Gal beta 1-4Man, and PO4-6(Ara beta 1-2Gal beta 1-3)Gal beta 1-4Man. These glycans are also components of the parasite glycolipid lipophosphoglycan, but their relative abundance and structural organization in PPG are different. Some of them represent novel forms of protein glycosylation. P-31 NMR on native PPG demonstrates that phosphate is exclusively in phosphodiester bonds and that the basic structure R-Man alpha 1-PO4-6-Gal-R connects the glycans. A phosphodiester linkage to phosphoserine (most likely R-Man alpha 1-PO4-Ser) anchors the PPG oligosaccharides to the polypeptide. PPG has a unique amino acid composition; glycosylated phosphoserine (>43 mol %), serine, alanine, and proline account for more than 87 mol % and appear to be clustered in large proteinase-resistant domains. Electron microscopy of purified PPG reveals cable-like, flexible, long (to 6 mu m), and unbranched filaments. The overall structure of PPG shows many similarities to mammalian mucins. Potential functions of this novel mucin-like molecule for the parasites are discussed.