Thornton D J, Devine P L, Hanski C, Howard M, Sheehan J K
Division of Biochemistry, School of Biological Sciences, University of Manchester, UK.
Am J Respir Crit Care Med. 1994 Sep;150(3):823-32. doi: 10.1164/ajrccm.150.3.8087358.
Two populations of reduced subunits were present in the mucins purified from pooled normal secretions and asthmatic and chronic bronchitic sputa; their relative level differed between samples. To investigate the nature of this heterogeneity, an asthmatic respiratory mucin preparation from a single individual was reduced and alkylated with 14C-iodoacetamide. This preparation was analyzed by gel filtration, agarose gel electrophoresis, immunoblotting, rate-zonal- and density-gradient centrifugation, and HPLC ion-exchange- and reverse-phase chromatography. Two populations (A and B) of reduced mucin subunits and a high-M(r)protein-rich fraction were identified. Species A has the higher molecular mass, is slowest migrating on agarose electrophoresis, has longer oligosaccharide chains, and expresses the carbohydrate structure sialyl-Le(x). Species B has a lower molecular mass, migrates faster in agarose electrophoresis Species B has a lower molecular mass, migrates faster in agarose electrophoresis, has shorter chains, and does not express sialyl-Le(x). The two subunits have similar but not identical amino acid compositions and 14C-tryptic peptide maps indicating they have different protein cores. The anti-sialyl-Le(x) antibody selectively precipitated subunit A not only from the reduced but also from the nonreduced mucin preparation, demonstrating that subunits A and B are present in different intact mucins.
从正常混合分泌物、哮喘和慢性支气管炎痰液中纯化的黏蛋白存在两种还原亚基群体；不同样本中它们的相对水平有所差异。为研究这种异质性的本质，对来自单个个体的哮喘呼吸道黏蛋白制剂进行还原并用14C-碘乙酰胺烷基化。通过凝胶过滤、琼脂糖凝胶电泳、免疫印迹、速率区带离心和密度梯度离心以及高效液相色谱离子交换和反相色谱对该制剂进行分析。鉴定出还原黏蛋白亚基的两个群体（A和B）以及一个富含高分子量（M(r)）蛋白质的组分。A类亚基分子量较高，在琼脂糖电泳中迁移最慢，具有较长的寡糖链，并表达碳水化合物结构唾液酸化路易斯寡糖（sialyl-Le(x)）。B类亚基分子量较低，在琼脂糖电泳中迁移较快，具有较短的链，且不表达唾液酸化路易斯寡糖（sialyl-Le(x)）。这两个亚基具有相似但不完全相同的氨基酸组成和14C-胰蛋白酶肽图谱，表明它们具有不同的蛋白质核心。抗唾液酸化路易斯寡糖（sialyl-Le(x)）抗体不仅能从还原的黏蛋白制剂中选择性沉淀出亚基A，也能从未还原的黏蛋白制剂中沉淀出亚基A，这表明亚基A和B存在于不同的完整黏蛋白中。
