Rio M C, Lepage P, Diemunsch P, Roitsch C, Chambon P
Laboratoire de Génétique moléculaire des Eucaryotes du C.N.R.S., Strasbourg.
C R Acad Sci III. 1988;307(19):825-31.
We have previously reported that pS2 mRNA expressed in cultured epithelial cells derived from a hormone-dependent breast carcinoma (MCF-7 cells) is also expressed in mucosa cells of normal human stomach. This mRNA encodes a putative 84 amino-acid-long protein, which is secreted by both cell types after elimination of a signal peptide. We report here the purification of the pS2 protein, its trypsin digestion and amino-acid sequencing. The MCF-7 cell-secreted protein is 60 amino-acid-long and its sequence is in complete agreement with that deduced from the mRNA sequence. The presence of an N-terminal glutamic acid indicates that the signal peptidase releases a 24 amino-acid-long signal peptide. Analysis of tryptic peptides derived from the secreted gastric pS2 protein indicates that the signal peptide and the sequence of the first 48 amino-acids are identical to those of secreted MCF-7 pS2 protein, although the N-terminal amino-acid of the gastric protein may be cyclized as a pyroglumatic acid.
我们先前曾报道，在源自激素依赖性乳腺癌的培养上皮细胞（MCF-7细胞）中表达的pS2 mRNA，在正常人胃黏膜细胞中也有表达。该mRNA编码一种推测的84个氨基酸长的蛋白质，在去除信号肽后，两种细胞类型均可分泌该蛋白。我们在此报告pS2蛋白的纯化、胰蛋白酶消化及氨基酸测序。MCF-7细胞分泌的蛋白为60个氨基酸长，其序列与从mRNA序列推导的序列完全一致。N端谷氨酸的存在表明信号肽酶释放了一个24个氨基酸长的信号肽。对源自分泌型胃pS2蛋白的胰蛋白酶肽段分析表明，信号肽及前48个氨基酸的序列与分泌型MCF-7 pS2蛋白的序列相同，尽管胃蛋白的N端氨基酸可能环化为焦谷氨酸。
