A heavily glycosylated membrane glycoprotein (mucin-1, polymorphic epithelial mucin, PEM, epithelial membrane antigen, EMA) encoded by the MUC1 gene; has a molecular weight of ~300 kDa, more than half of which is O-linked glycan. There is a 69 aa cytoplasmic domain and the extracellular N-terminal portion has variable numbers of 20-aa tandem repeats that are extensively modified by O-linked glycans and may extend hundreds of nanometres beyond the plasma membrane. The normal role may be to inhibit bacterial adhesion to mucous membranes but increased expression in carcinoma cells may reduce their adhesion and mask the antigenic properties of the cells. Similar functions are ascribed to ASGP, epiglycanin, and leukosialin.
Subjects: Medicine and Health.