AglJ Adds the First Sugar of the N-Linked Pentasaccharide Decorating the Haloferax volcanii S-Layer Glycoprotein
AglJ Adds the First Sugar of the N-Linked Pentasaccharide Decorating the Haloferax volcanii S-Layer Glycoprotein
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DOI：
10.1128/jb.00705-10
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发表时间：
2010-11-01
影响因子：
3.2
通讯作者：
Eichler, Jerry
中科院分区：
文献类型：
--
作者：
Kaminski, Lina;Abu-Qarn, Mehtap;Eichler, Jerry
与真核生物和细菌一样，古细菌也进行 N 糖基化。使用haloarchaeon Haloferax volcanii作为模型系统，已经鉴定出参与这种翻译后修饰的古菌版本的一系列Agl蛋白。在本研究中，考虑到 HVO_1517 参与 N 糖基化，因为它与真核 N-糖基化途径的已知成分同源，并且因为 HVO_1517 与编码 H. volcanii N-糖基化过程的已知元件的 agl 基因基因组接近。通过将 HVO_1517 的删除与多羟基磷酸单糖负载载体和 S 层糖蛋白的质谱分析相结合，获得的证据表明 HVO_1517（更名为 AglJ）参与添加装饰该报告糖蛋白的 N-连接五糖的第一个己糖。然而，aglJ 的缺失并不能完全阻止己糖残基与 S 层糖蛋白的附着。此外，在没有 AglJ 的情况下，细胞中检测到的三种带单糖的多甘醇磷酸盐载体中只有一种的水平降低。尽管如此，在缺乏 AglJ 的细胞中，没有进一步的糖亚基被添加到剩余的带单糖的多甘醇磷酸载体或单糖修饰的 S 层糖蛋白中，这表明通过 AglJ 的作用添加的糖对于正确的 N 糖基化非常重要。最后，虽然 aglJ 可以被删除，但在缺乏编码蛋白的情况下，H. volcanii 表面层的完整性会受到损害。
Like the Eukarya and Bacteria, the Archaea also perform N glycosylation. Using the haloarchaeon Haloferax volcanii as a model system, a series of Agl proteins involved in the archaeal version of this posttranslational modification has been identified. In the present study, the participation of HVO_1517 in N glycosylation was considered, given its homology to a known component of the eukaryal N-glycosylation pathway and because of the genomic proximity of HVO_1517 to agl genes encoding known elements of the H. volcanii N-glycosylation process. By combining the deletion of HVO_1517 with mass spectrometric analysis of both dolichol phosphate monosaccharide-charged carriers and the S-layer glycoprotein, evidence was obtained showing the participation of HVO_1517, renamed AglJ, in adding the first hexose of the N-linked pentasaccharide decorating this reporter glycoprotein. The deletion of aglJ, however, did not fully prevent the attachment of a hexose residue to the S-layer glycoprotein. Moreover, in the absence of AglJ, the level of only one of the three monosaccharide-charged dolichol phosphate carriers detected in the cell was reduced. Nonetheless, in cells lacking AglJ, no further sugar subunits were added to the remaining monosaccharide-charged dolichol phosphate carriers or to the monosaccharide-modified S-layer glycoprotein, pointing to the importance of the sugar added through the actions of AglJ for proper N glycosylation. Finally, while aglJ can be deleted, H. volcanii surface layer integrity is compromised in the absence of the encoded protein.