Lewis M J, Turco S J, Green M
J Biol Chem. 1985 Jun 10;260(11):6926-31.
We have studied the post-translational processing and the biosynthetic sorting of three protein components of murine endoplasmic reticulum (ER), ERp60, ERp72, and ERp99. In pulse-labeled MOPC-315 (where MOPC-315 represents mineral oil-induced plasmacytoma cells) plasmacytoma cells, no precursor forms of these proteins were detected and only ERp99 was sensitive to endoglycosidase H. The ERp99 oligosaccharide remained endoglycosidase H sensitive during a 3-h chase, and analysis by high performance liquid chromatography showed the predominant structure to be Man8GlcNAc2. We have used a sucrose gradient analysis of pulse-labeled MOPC-315 plasmacytoma cells in order to directly study the biosynthetic sorting of both glycosylated and nonglycosylated ERps and have found no strong evidence to suggest these proteins ever leave the endoplasmic reticulum. In spite of their common sorting pathway, these proteins differ in their membrane orientation. Both ERp60 and ERp72 are entirely protected by the endoplasmic reticulum membrane while ERp99 appears to have a large domain exposed on the cytoplasmic face of the endoplasmic reticulum.
我们研究了小鼠内质网（ER）的三种蛋白质成分ERp60、ERp72和ERp99的翻译后加工及生物合成分选过程。在脉冲标记的MOPC - 315（其中MOPC - 315代表矿物油诱导的浆细胞瘤细胞）浆细胞瘤细胞中，未检测到这些蛋白质的前体形式，且只有ERp99对内切糖苷酶H敏感。在3小时的追踪过程中，ERp99的寡糖对内切糖苷酶H仍保持敏感，高效液相色谱分析表明其主要结构为Man8GlcNAc2。为了直接研究糖基化和非糖基化ERp的生物合成分选，我们对脉冲标记的MOPC - 315浆细胞瘤细胞进行了蔗糖梯度分析，未发现有力证据表明这些蛋白质曾离开内质网。尽管它们有共同的分选途径，但这些蛋白质的膜取向不同。ERp60和ERp72完全被内质网膜保护，而ERp99似乎有一个大的结构域暴露在内质网的细胞质面上。
