Price M R, Hudecz F, O'Sullivan C, Baldwin R W, Edwards P M, Tendler S J
Cancer Research Campaign Laboratories, University of Nottingham, University Park, U.K.
Mol Immunol. 1990 Aug;27(8):795-802. doi: 10.1016/0161-5890(90)90089-i.
The protein core of high mol. wt polymorphic epithelial mucin (PEM--approximately 400 kDa glycoprotein) which is associated with breast carcinomas, consists of a repeating 20 amino acid peptide motif [Gendler et al. (1988) J. biol. Chem. 263, 12,820-12,823]. Monoclonal antibodies C595 (anti-urinary mucin) and NCRC-11 (anti-breast carcinoma cells), and other antibodies against human milk fat globule membranes, were found to recognize determinants present within this 20 amino acid peptide. A model of the peptide was developed based on hydropathicity and structure prediction calculations and these indicated that the repeated structure is dominated by a hydrophilic domain of seven amino acids, extending into two flanking beta turns. NMR analysis of the 20 amino acid peptide was undertaken to probe the secondary structure. Epitope mapping experiments involving solid phase synthesis of overlapping heptapeptides in the repeat unit identified the minimum structures for antibody binding as Arg-Pro-Ala-Pro and Arg-Pro-Ala for the C595 and NCRC-11 antibodies, respectively. These determinants were found within the predicted hydrophilic turn region domain of the peptide. The epitopes for six other PEM-reactive monoclonal antibodies were also determined to reside within the predicted hydrophilic turn domain. This evidence is in accord with the disposition of this region of the PEM peptide core being at the exterior of the glycoprotein where it would be accessible to antibody recognition and binding events.
高分子量多态性上皮粘蛋白（PEM，一种约400 kDa的糖蛋白）的蛋白质核心与乳腺癌相关，它由一个重复的20个氨基酸的肽基序组成[Gendler等人（1988年）《生物化学杂志》263卷，12820 - 12823页]。发现单克隆抗体C595（抗尿粘蛋白）和NCRC - 11（抗乳腺癌细胞）以及其他针对人乳脂肪球膜的抗体能够识别这个20个氨基酸肽内的决定簇。基于亲水性和结构预测计算构建了该肽的模型，结果表明重复结构主要由一个七个氨基酸的亲水区主导，延伸到两个侧翼β转角中。对该20个氨基酸的肽进行了核磁共振分析以探究其二级结构。涉及在重复单元中固相合成重叠七肽的表位作图实验确定了C595和NCRC - 11抗体结合的最小结构分别为Arg - Pro - Ala - Pro和Arg - Pro - Ala。这些决定簇位于该肽预测的亲水性转角区域内。还确定了其他六种与PEM反应的单克隆抗体的表位也位于预测的亲水性转角区域内。这一证据与PEM肽核心的该区域位于糖蛋白外部的情况相符，在那里它可被抗体识别和结合。
