Mazzarella R A, Green M
J Biol Chem. 1987 Jun 25;262(18):8875-83.
We have isolated an expressible full-length cDNA clone encoding murine ERp99, an abundant, conserved transmembrane glycoprotein of the endoplasmic reticulum membrane. ERp99 is synthesized as a 92,475-kDa precursor containing 802 amino acids. It possesses a signal peptide of 21 amino acids which is cleaved cotranslationally. Analysis of the amino acid sequence deduced from the nucleotide sequence of the cDNA clone led us to propose a model for the orientation of ERp99 in the endoplasmic reticulum membrane. In this model, ERp99 possesses one membrane-spanning, stop transfer segment in the N-terminal region. The protein chain passes through the membrane only once, and approximately 75% of the protein remains on the cytoplasmic side of the ER membrane. Comparison of the ERp99 sequence to the sequence of other proteins revealed that ERp99 has extensive homology with the 90-kDa heat shock protein of Saccharomyces cerevisiae (hsp90) and the 83-kDa heat shock protein of Drosophila melanogaster. In addition, the N terminus of mature ERp99 is identical to that of the 94-kDa glucose regulated protein (GRP94) of mammalian cells.
我们分离出了一个可表达的全长cDNA克隆，其编码小鼠内质网蛋白99（ERp99），这是一种内质网膜中含量丰富、保守的跨膜糖蛋白。ERp99最初被合成为一个含有802个氨基酸、分子量为92,475道尔顿的前体。它具有一个由21个氨基酸组成的信号肽，该信号肽在共翻译过程中被切割。对从cDNA克隆的核苷酸序列推导出来的氨基酸序列进行分析后，我们提出了一个关于ERp99在内质网膜中取向的模型。在这个模型中，ERp99在N端区域有一个跨膜的终止转移片段。蛋白质链仅穿过膜一次，并且大约75%的蛋白质保留在内质网的细胞质一侧。将ERp99的序列与其他蛋白质的序列进行比较后发现，ERp99与酿酒酵母的90 kDa热休克蛋白（hsp90）以及黑腹果蝇的83 kDa热休克蛋白具有广泛的同源性。此外，成熟ERp99的N端与哺乳动物细胞的94 kDa葡萄糖调节蛋白（GRP94）的N端相同。
