OST4 is a subunit of the mammalian oligosaccharyltransferase required for efficient N-glycosylation.
OST4 is a subunit of the mammalian oligosaccharyltransferase required for efficient N-glycosylation.
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DOI：
10.1242/jcs.115410
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发表时间：
2013-06-15
影响因子：
4
通讯作者：
High S
中科院分区：
文献类型：
--
作者：
Dumax-Vorzet A;Roboti P;High S
真核寡糖基转移酶（OST）是一种膜包埋的蛋白复合物，其催化内质网（ER）内腔中新生多肽的N-糖基化，这是一种高度保守的生物合成过程，其丰富蛋白质结构和功能。所有OST都含有催化STT 3亚基的同源物，尽管在许多情况下，这与影响功能的几个额外组件组装在一起。In S.在酿酒酵母中，一种这样的组分是Ost 4p，一种非常小的膜蛋白，其似乎稳定组装的OST复合物的亚基之间的相互作用。OST 4已被鉴定为推定的人类同源物，但迄今为止，它与OST复合物的关系，也没有它在蛋白质N-糖基化中的作用，已被直接解决。在这里，我们确定OST 4组装成含有催化STT 3A或STT 3B同种型的天然OST复合物。免疫共沉淀研究表明，OST 4与STT 3亚型和核糖体蛋白I（哺乳动物OST的辅助亚基）相关。这些假定的相互作用受到OST 4跨膜区中单个氨基酸变化的干扰。使用siRNA敲除和天然凝胶分析，我们表明OST 4在维持天然OST复合物的稳定性方面起着重要作用。因此，在OST 4耗尽明确的OST复合物是部分不稳定的，可以检测到一种新的含核糖核酸酶I的亚复合物。引人注目的是，耗尽OST 4或STT 3A的细胞在内源性鞘脂激活蛋白原的N-糖基化中显示出非常相似的缺陷。我们的结论是，OST 4最有可能促进共翻译N-糖基化稳定STT 3A的OST亚型。
The eukaryotic oligosaccharyltransferase (OST) is a membrane-embedded protein complex that catalyses the N-glycosylation of nascent polypeptides in the lumen of the endoplasmic reticulum (ER), a highly conserved biosynthetic process that enriches protein structure and function. All OSTs contain a homologue of the catalytic STT3 subunit, although in many cases this is assembled with several additional components that influence function. In S. cerevisiae, one such component is Ost4p, an extremely small membrane protein that appears to stabilise interactions between subunits of assembled OST complexes. OST4 has been identified as a putative human homologue, but to date neither its relationship to the OST complex, nor its role in protein N-glycosylation, have been directly addressed. Here, we establish that OST4 is assembled into native OST complexes containing either the catalytic STT3A or STT3B isoforms. Co-immunoprecipitation studies suggest that OST4 associates with both STT3 isoforms and with ribophorin I, an accessory subunit of mammalian OSTs. These presumptive interactions are perturbed by a single amino acid change in the transmembrane region of OST4. Using siRNA knockdowns and native gel analysis, we show that OST4 plays an important role in maintaining the stability of native OST complexes. Hence, upon OST4 depletion well-defined OST complexes are partially destabilised and a novel ribophorin I-containing subcomplex can be detected. Strikingly, cells depleted of either OST4 or STT3A show a remarkably similar defect in the N-glycosylation of endogenous prosaposin. We conclude that OST4 most likely promotes co-translational N-glycosylation by stabilising STT3A-containing OST isoforms.
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DOI：
10.1073/pnas.94.10.4994
发表时间：
1997-05-13
影响因子：
11.1
作者：
Kelleher, DJ;Gilmore, R
通讯作者：
Gilmore, R
影响因子：
4.8
作者：
Fu, J;Ren, MD;Kreibich, G
通讯作者：
Kreibich, G
影响因子：
5.3
作者：
Dekker, PJT;Ryan, MT;Pfanner, N
通讯作者：
Pfanner, N
影响因子：
82.9
作者：
Honma, Kimi;Iwao-Koizumi, Kyoko;Ochiya, Takahiro
通讯作者：
Ochiya, Takahiro
影响因子：
16
作者：
Kelleher, DJ;Karaoglu, D;Gilmore, R
通讯作者：
Gilmore, R