Masaki R, Yamamoto A, Akagawa K, Tashiro Y
Department of Physiology, and Cell Biology Division of Liver Research Center, Kansai Medical University, Moriguchi, Osaka, 570-8506, Japan.
J Biochem. 1998 Aug;124(2):311-8. doi: 10.1093/oxfordjournals.jbchem.a022113.
HPC-1/syntaxin 1A (HPC-1), which plays an important role in vesicular transport to the plasma membrane, possesses a hydrophobic sequence at its C terminus. When expressed from cDNA in COS cells, wild-type HPC-1 was localized in the Golgi complex and the plasma membrane. Truncation of the hydrophobic domain resulted in the cytoplasmic localization of the mutant, thus indicating that the domain indeed functions as a membrane anchor. A fusion protein with the C-terminal glycosylation sites was glycosylated in transfected cells, providing evidence that HPC-1 has a transmembrane structure, and that the protein is first inserted into the endoplasmic reticulum and then transported to the plasma membrane. A chimeric protein consisting of Escherichia coli maltose-binding protein with the last 24 amino acids of HPC-1 was inserted into the endoplasmic reticulum in a transmembrane topology and localized along the exocytic pathway of transfected cells similar to HPC-1. These results indicate that the portion is important for intracellular localization of HPC-1.
HPC-1/ syntaxin 1A（HPC-1）在囊泡向质膜的转运中起重要作用，其C末端具有一个疏水序列。当从cDNA在COS细胞中表达时，野生型HPC-1定位于高尔基体复合物和质膜。疏水结构域的截断导致突变体定位于细胞质，从而表明该结构域确实起到膜锚的作用。具有C末端糖基化位点的融合蛋白在转染细胞中被糖基化，这证明HPC-1具有跨膜结构，并且该蛋白首先插入内质网，然后转运到质膜。由大肠杆菌麦芽糖结合蛋白与HPC-1的最后24个氨基酸组成的嵌合蛋白以跨膜拓扑结构插入内质网，并与HPC-1类似地沿着转染细胞的胞吐途径定位。这些结果表明该部分对于HPC-1的细胞内定位很重要。
