Receptor-mediated transcellular transport of immunoglobulin: synthesis of secretory component as multiple and larger transmembrane forms.

摘要: We have characterized the early biosynthetic forms of secretory component (SC). SC is synthesized in various glandular epithelial cells and functions transepithelial transport certain polymeric immunoglobulins. In rabbit, mature known to be heterogeneous, consisting two or three immunologically related glycoproteins. Using translation mRNA from rabbit mammary gland liver a wheat germ cell-free system supplemented with dog pancreas microsomal vesicles, we discovered that products include at least four distinct polypeptides. Moreover, found all polypeptides are not as soluble but considerably larger transmembrane core-glycosylated asymmetrically integrated into vesicles translation-coupled manner. therefore conclude secreted endoproteolytic fragments derived comprising ectoplasmic portion precursor forms. The detection for provides protein structural basis their function receptors mediating immuno-globulin molecules.