Meyer Urs, Fraering Patrick, Bosson Régine, Imhof Isabella, Benghezal Mohammed, Vionnet Christine, Conzelmann Andreas
Institute of Biochemistry, University of Fribourg, Switzerland.
Mol Microbiol. 2002 Nov;46(3):745-8. doi: 10.1046/j.1365-2958.2002.03192.x.
Biosynthesis of glycosylphosphatidylinositol (GPI)-anchored proteins involves the action of a GPI trans-amidase, which replaces the C-terminal GPI signal sequence (GPI-SS) of the primary translation product with a preformed GPI lipid. The transamidation depends on a complex of four proteins, Gaa1p, Gpi8p, Gpi16p and Gpi17p. Although the GPI anchoring pathway is conserved throughout the eukaryotic kingdom, it has been reported recently that the GPI-SS of human placental alkaline phosphatase (hPLAP) is not recognized by the yeast transamidase, but is recognized in yeast that contain the human Gpi8p homologue. This finding suggests that Gpi8p is intimately involved in the recognition of GPI precursor proteins and may also be responsible for the subtle taxon-specific differences in transamidase specificity that sometimes prevent the efficient GPI anchoring of heterologously expressed GPI proteins. Here, we confirm that the GPI signal sequence of hPLAP is indeed not recognized by the yeast GPI-anchoring machinery. However, in our hands, GPI attachment cannot be restored by the co-expression of human Gpi8p in yeast cells under any circumstances.
糖基磷脂酰肌醇（GPI）锚定蛋白的生物合成涉及GPI转酰胺酶的作用，该酶用预先形成的GPI脂质取代初级翻译产物的C末端GPI信号序列（GPI-SS）。转酰胺作用依赖于四种蛋白质Gaa1p、Gpi8p、Gpi16p和Gpi17p的复合物。尽管GPI锚定途径在整个真核生物界是保守的，但最近有报道称，人胎盘碱性磷酸酶（hPLAP）的GPI-SS不被酵母转酰胺酶识别，但在含有人类Gpi8p同源物的酵母中被识别。这一发现表明，Gpi8p密切参与GPI前体蛋白的识别，也可能是转酰胺酶特异性中细微的分类群特异性差异的原因，这些差异有时会阻止异源表达的GPI蛋白的有效GPI锚定。在这里，我们证实hPLAP的GPI信号序列确实不被酵母GPI锚定机制识别。然而，在我们的实验中，在任何情况下，人Gpi8p在酵母细胞中的共表达都不能恢复GPI连接。
