Gendler S J, Lancaster C A, Taylor-Papadimitriou J, Duhig T, Peat N, Burchell J, Pemberton L, Lalani E N, Wilson D
Imperial Cancer Research Fund, Lincoln's Inn Fields, London, United Kingdom.
J Biol Chem. 1990 Sep 5;265(25):15286-93.
Human mammary cells present on the cell surface a polymorphic epithelial mucin (PEM) which is developmentally regulated and aberrantly expressed in tumors. PEM carries tumor-associated epitopes recognized by the monoclonal antibodies HMFG-1, HMFG-2, and SM-3. Previously isolated partial cDNA clones revealed that the core protein contained a large domain consisting of variable numbers of 20-amino acid repeat units. We now report the full sequence for PEM, as deduced from cDNA sequences. The encoded protein consists of three distinct regions: the amino terminus consisting of a putative signal peptide and degenerate repeats; the major portion of the protein which is the tandem repeat region; the carboxyl terminus consisting of degenerate tandem repeats and a unique sequence containing a transmembrane sequence and a cytoplasmic tail. Potential O-glycosylation sites (serines or threonines) make up more than one-fourth of the amino acids. Length variations in the tandem repeat result in PEM being an expressed variable number tandem repeat locus. Tandem repeats appear to be a general characteristic of mucin core proteins.
人乳腺细胞在细胞表面呈现一种多态性上皮粘蛋白（PEM），它在发育过程中受到调控，在肿瘤中异常表达。PEM携带被单克隆抗体HMFG - 1、HMFG - 2和SM - 3识别的肿瘤相关表位。先前分离的部分cDNA克隆显示，核心蛋白包含一个由可变数量的20个氨基酸重复单元组成的大结构域。我们现在报告从cDNA序列推导出来的PEM的完整序列。编码的蛋白质由三个不同区域组成：氨基末端由一个推定的信号肽和简并重复序列组成；蛋白质的主要部分是串联重复区域；羧基末端由简并串联重复序列和一个包含跨膜序列和细胞质尾巴的独特序列组成。潜在的O - 糖基化位点（丝氨酸或苏氨酸）占氨基酸的四分之一以上。串联重复序列的长度变化导致PEM成为一个表达的可变数量串联重复基因座。串联重复似乎是粘蛋白核心蛋白的一个普遍特征。
