CHARACTERIZATION OF O-LINKED GLYCOSYLATION MOTIFS IN THE GLYCOPEPTIDE DOMAIN OF BOVINE KAPPA-CASEIN

kappa-Casein is the major glycoprotein in bovine milk, It has a proteinase-sensitive (chymosin) site which cleaves the glycoprotein into two segments: N-terminal-para-kappa-casein domain and the C-terminal kappa-casein macroglycopeptide domain which is highly heterogeneous in oligosaccharide content, We have identified six sites of O-glycosylation on the macroglycopeptide by solid-phase Edman degradation: Thr121, Thr131, Thr133, Thr136 (A variant only), Thr142 and Thr165. No Ser residues are glycosylated, The glycosylation status of 15 of 17 potential O-glycosylation sites in the B variant was accurately predicted using the four peptide moths previously proposed for the glycosylation of human glycophorin A (Pisano, A., Redmond, J. W., Williams, K. L. and Gooley, A. A., Glycobiology, 3, 429-435, 1993), provided one additional assumption is made concerning an inhibitory role for a nearby Ile.