Ethanolamine Phosphate Linked to the First Mannose Residue of Glycosylphosphatidylinositol (GPI) Lipids Is a Major Feature of the GPI Structure That Is Recognized by Human GPI Transamidase*
Ethanolamine Phosphate Linked to the First Mannose Residue of Glycosylphosphatidylinositol (GPI) Lipids Is a Major Feature of the GPI Structure That Is Recognized by Human GPI Transamidase*
复制标题
与糖基磷脂酰肌醇 (GPI) 脂质的第一个甘露糖残基连接的磷酸乙醇胺是人 GPI 转酰胺酶识别的 GPI 结构的主要特征*
DOI：
10.1074/jbc.m608896200
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发表时间：
2006
影响因子：
4.8
通讯作者：
A. Menon
中科院分区：
文献类型：
--
作者：
S. Vainauskas;A. Menon
糖基磷脂酰肌醇（GPI）锚定蛋白是由GPI转氨酶（GPIT）催化的，GPI转氨酶是一种多亚基内质网（ER）定位酶。GPIT识别具有GPI定向c端信号序列的er易位蛋白，并用预组装的GPI锚点取代该序列。虽然GPI信号序列已被广泛表征，但很少有人知道GPI脂质底物的结构特征，使其能够被GPIT识别。在之前的一项研究中，我们发现成熟的gpi可以与含有功能亚基的GPIT复合物共同免疫沉淀(Vainauskas， S., and Menon, a . K. (2004) J. Biol。化学，279,6540-6545)。我们现在使用这种方法，以及一种重建GPI和GPIT之间相互作用的方法，来定义GPI和人类GPIT之间相互作用的基础。我们报道(i)人类GPIT可以与GPI生物合成中间体相互作用，而不仅仅是成熟的GPI能够转移到蛋白质上，（ii） GPI聚糖的第三个甘露糖残基上的乙醇胺磷酸基团对于GPIT识别GPI不是至关重要的，（iii）与GPI结构的第一个甘露糖相连的乙醇胺磷酸残基是GPI被人类GPIT识别的主要特征。（iv）人类GPIT识别的最简单的GPI是EtN-P-2Manα1-4GlcN -（酰基）-磷脂酰肌醇。这些研究明确了GPIT识别的GPI分子特征，并为识别参与该过程的GPIT亚基开辟了道路。
Glycosylphosphatidylinositol (GPI) anchoring of proteins is catalyzed by GPI transamidase (GPIT), a multisubunit, endoplasmic reticulum (ER)-localized enzyme. GPIT recognizes ER-translocated proteins that have a GPI-directing C-terminal signal sequence and replaces this sequence with a preassembled GPI anchor. Although the GPI signal sequence has been extensively characterized, little is known about the structural features of the GPI lipid substrate that enable its recognition by GPIT. In a previous study we showed that mature GPIs could be co-immunoprecipitated with GPIT complexes containing functional subunits (Vainauskas, S., and Menon, A. K. (2004) J. Biol. Chem. 279, 6540–6545). We now use this approach, as well as a method that reconstitutes the interaction between GPIs and GPIT, to define the basis of the interaction between GPI and human GPIT. We report that (i) human GPIT can interact with GPI biosynthetic intermediates, not just mature GPIs competent for transfer to protein, (ii) the ethanolamine phosphate group on the third mannose residue of the GPI glycan is not critical for GPI recognition by GPIT, (iii) the ethanolamine phosphate residue linked to the first mannose of the GPI structure is a major feature of GPIs that is recognized by human GPIT, and (iv) the simplest GPI recognized by human GPIT is EtN-P-2Manα1–4GlcN-(acyl)-phosphatidyl-inositol. These studies define the molecular characteristics of GPI that are recognized by GPIT and open the way to identifying GPIT subunits that are involved in this process.