Unique N-Glycan Moieties of the 66-kDa Cell Wall Glycoprotein from the Red Microalga Porphyridium sp.
Unique N-Glycan Moieties of the 66-kDa Cell Wall Glycoprotein from the Red Microalga Porphyridium sp.
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DOI：
10.1074/jbc.m110.175042
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发表时间：
2011-06-17
影响因子：
4.8
通讯作者：
Tekoah, Yoram
中科院分区：
文献类型：
--
作者：
Levy-Ontman, Oshrat;Arad, Shoshana (Malis);Tekoah, Yoram
我们在这里报告了 66 kDa 糖蛋白中 N 连接聚糖的结构测定，该糖蛋白是红色微藻紫球藻独特的硫酸化复合细胞壁多糖的一部分。通过正相/反相 HPLC、正离子 MALDI-TOF MS、负离子电喷雾电离和 MS/MS 的组合来阐明结构。糖蛋白的糖部分由至少四个 N 连接聚糖部分组成，每个部分由相同的四种单糖组成：GlcNAc、Man、6-O-MeMan 和 Xyl，其组成为 Man(8-9)Xyl(1-2)Me(3)GlcNAc(2)。本研究首次报道了末端 Xyl 连接到 6-天线的 6-甘露糖分支和倒数第二个（核心）GlcNAc 的 3-氧的 N-聚糖。另一个新发现是，所有四种聚糖都含有三个 O-甲基甘露糖残基，其位置以前从未报道过。尽管已知一些低等生物能够甲基化聚糖中的末端单糖，但目前对紫球藻的研究。是第一个描述能够甲基化非末端甘露糖残基的生物体。因此，这项研究将有助于理解藻类中的 N-糖基化，并可能揭示从原核生物到多细胞生物的进化发展。它还可能有助于我们了解红藻多糖的形成。这项研究的额外重要性在于其生物技术应用的潜力，特别是在评估微藻作为细胞工厂生产治疗性蛋白质的用途方面。
We report here the structural determination of the N-linked glycans in the 66-kDa glycoprotein, part of the unique sulfated complex cell wall polysaccharide of the red microalga Porphyridium sp. Structures were elucidated by a combination of normal phase/reverse phase HPLC, positive ion MALDI-TOF MS, negative ion electrospray ionization, and MS/MS. The sugar moieties of the glycoprotein consisted of at least four fractions of N-linked glycans, each composed of the same four monosaccharides, GlcNAc, Man, 6-O-MeMan, and Xyl, with compositions Man(8-9)Xyl(1-2)Me(3)GlcNAc(2). The present study is the first report of N-glycans with the terminal Xyl attached to the 6-mannose branch of the 6-antenna and to the 3-oxygen of the penultimate (core) GlcNAc. Another novel finding was that all four glycans contain three O-methylmannose residues in positions that have never been reported before. Although it is known that some lower organisms are able to methylate terminal monosaccharides in glycans, the present study on Porphyridium sp. is the first describing an organism that is able to methylate non-terminal mannose residues. This study will thus contribute to understanding of N-glycosylation in algae and might shed light on the evolutionary development from prokaryotes to multicellular organisms. It also may contribute to our understanding of the red algae polysaccharide formation. The additional importance of this research lies in its potential for biotechnological applications, especially in evaluating the use of microalgae as cell factories for the production of therapeutic proteins.