Biochemistry and molecular biology of MCA

The mucin-like carcinoma-associated antigen (MCA) is a mucin with a molecular weight of 350-500 kD. It circulates in the serum and its serum content can be determined with the Cobas Core MCA EIA test. Patients with breast cancer show elevated MCA serum levels. The molecule has a polypeptide backbone consisting of three parts: the C-terminus the N-terminus and the transmembrane sequences. The protein is heavily glucosylated with carbohydrate side chains that contain fucose, galactose and N-acetyl galactosamine. The antibody b-12 recognizes a repetitive epitope on the peptide portion of the MCA molecule. The epithelial mucin, which is coded by a unique gene, was cloned using PCR technology. Peptides corresponding to the N- and C-terminus were expressed in E. coli. Analysis of the purified peptides revealed molecular weights of 12 and 18 kD.