During translation, MUC1 is cleaved into two domains, MUC1-N and MUC1-C. MUC1-N consists predominantly of the TR domain and the sequence of a single repeat is illustrated. The TR domain is glycosylated with O-linked glycans (in red) and each repeat has five potential sites shown in bold. There are also sites for O-linked glycosylation in the degenerate TRs located to the N- and C-termini of the repeats. There are five potential sites for N-linked glycosylation close to the membrane (in black). MUC1-C consists of 58 amino acids of the external domain, the transmembrane domain (in blue, 28 aa) and the cytoplasmic domain (MUC1-CD, 72 aa). Within the CD1 domain, the CQC trimer is responsible for homodimerization. There are many phosphorylation sites within the CD domain and two of these are indicated. The CQC containing peptide (GO-232) targets the homodimerization domain.