Keenan T W, Winter S, Rackwitz H R, Heid H W
Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
Biochim Biophys Acta. 2000 Sep 1;1523(1):84-90. doi: 10.1016/s0304-4165(00)00106-9.
We have identified the p100 protein, previously known as a novel cellular coactivator, as a constituent of endoplasmic reticulum and cytosolic lipid droplets from milk secreting cells. Cytosolic lipid droplets of terminally differentiated mammary epithelial cells are secreted as milk lipid globules. However, milk lipid globules did not have detectable amounts of p100 protein. The p100 protein was found also in cytosol from lactating mammary gland, in storage lipid droplets from mouse adipocytes, and in endoplasmic reticulum from liver. Immunofluorescence microscopy of mammary epithelial cells confirmed the presence of p100 in non-nuclear regions of these cells. Partial sequence analysis of tryptic peptides from p100 from cow mammary gland showed extensive homology with the reported sequence of p100 determined from a human cDNA. Antibodies against a peptide synthesized to duplicate a sequence in human p100 recognized a protein of the size of p100 in cow, mouse and rat cell fractions.
我们已确定p100蛋白（以前被认为是一种新型细胞辅激活因子）是来自泌乳细胞的内质网和胞质脂滴的组成成分。终末分化乳腺上皮细胞的胞质脂滴会作为乳脂肪球分泌出来。然而，乳脂肪球中未检测到p100蛋白。在泌乳乳腺的胞质溶胶、小鼠脂肪细胞的储存脂滴以及肝脏的内质网中也发现了p100蛋白。乳腺上皮细胞的免疫荧光显微镜检查证实这些细胞的非核区域存在p100蛋白。对来自牛乳腺的p100胰蛋白酶肽段进行的部分序列分析显示，其与从人cDNA确定的p100报道序列具有广泛的同源性。针对合成的与人p100序列重复的肽段产生的抗体，在牛、小鼠和大鼠细胞组分中识别出了p100大小的蛋白。
