Healthy human MUC1 is a highly glycosylated extracellular peptide, containing a highly conserved tandem repeat sequence of 20 amino acids (GVTSAPDTRPAPGSTAPPAH)). Tumour associated MUC1 ((TA)MUC1) shows enhanced expression in 90% of breast cancers . (TA)MUC1 is characterised by the incomplete glycosylation of the peptide backbone, resulting in a change of conformation and exposure of the peptide backbone to the immune system . Autoantibodies from the sera of patients bound specifically to the incompletely glycosylated Ser¹⁴ and Thr¹⁵ of the GSTA domain of the tandem repeat sequence . Seven glycopeptides were produced by solid phase peptide synthesis based off two regions of the MUC1 peptide sequence, one region containing Thr⁸ of the DTR region and the other containing Ser¹⁴ and Thr¹⁵ of the GSTA region. Each of the seven glycopeptides exhibits a different level of Tn antigen (α-GalNAc) expression.
Cholera toxin B-subunit has previously been investigated for the display of peptide antigens, but not for carbohydrate antigens . CTB-glycoconjugates of (TA)MUC1 were prepared using C-terminal sortase-mediated transpeptidase ligation methodology. These glycoconjugates were produced on a preparative scale and will go on to be used for the identification of antibody-like proteins via phag
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