Oligosaccharyltransferase isoforms that contain different catalytic STT3 subunits have distinct enzymatic properties
Oligosaccharyltransferase isoforms that contain different catalytic STT3 subunits have distinct enzymatic properties
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DOI：
10.1016/s1097-2765(03)00243-0
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发表时间：
2003-07-01
期刊：
影响因子：
16
通讯作者：
Gilmore, R
中科院分区：
文献类型：
--
作者：
Kelleher, DJ;Karaoglu, D;Gilmore, R
寡糖基转移酶（OST）是一种整合膜蛋白，它催化内质网腔中新生蛋白质的N -连接糖基化。尽管酵母中的OST是由非同源亚基（Ost1p、Ost2p、Ost3p/Ost6p、Ost4p、Ost5p、Wbp1p、Swp1p和Stt3p）组装而成的八聚体，但脊椎动物OST的组成尚不明确。特定OST亚基的作用仍然是个谜。在此我们表明，大多数多细胞真核生物的基因组编码两个Stt3p同源物，并且哺乳动物表达两个Ost3p同源物。Stt3p和Ost3p同源物与先前描述的哺乳动物OST亚基（核糖体结合蛋白I和II、OST48和DAD1）一起组装成在酶活性上有显著差异的复合物。Stt3p同源物表达的组织和细胞类型特异性差异表明，真核生物中寡糖基转移酶的酶学特性受到调控，以应对通过分泌途径的糖蛋白流量的变化，并可能导致组织特异性聚糖异质性。
Oligosaccharyltransferase (OST) is an integral membrane protein that catalyzes N-linked glycosylation of nascent proteins in the lumen of the endoplasmic reticulum. Although the yeast OST is an octamer assembled from nonhomologous subunits (Ost1p, Ost2p, Ost3p/Ost6p, Ost4p, Ost5p, Wbp1p, Swp1p, and Stt3p), the composition of the vertebrate OST was less well defined. The roles of specific OST subunits remained enigmatic. Here we show that genomes of most multicellular eukaryotes encode two homologs of Stt3p and mammals express two homologs of Ost3p. The Stt3p and Ost3p homologs are assembled together with the previously described mammalian OST subunits (ribophorins I and II, OST48, and DAD1) into complexes that differ significantly in enzymatic activity. Tissue and cell type-specific differences in expression of the Stt3p homologs suggest that the enzymatic properties of oligosaccharyltransferase are regulated in eukaryotes to respond to alterations in glycoprotein flux through the secretory pathway and may contribute to tissue-specific glycan heterogeneity.