Mucin glycoproteins on breast cancer cells carry shortened carbohydrate chains. These partially deglycosylatedmucin 1 (MUC-1) structures are recognized by the monoclonal antibody SM3, which is being tested for its diagnostic utility. We used NMR spectroscopy to analyze the binding mode and thebindingepitopeof peptideandglycopeptideantigens to the SM3 antibody. The pentapeptide PDTRP and the glycopentapeptide PDT(O-a-D-GalNAc)RP are known lig-ands of the monoclonal antibody.
