Synthesis of an N-linked glycopeptide from vitamin K-dependent protein S

Abstract

A novel asparagine building block having an N-linked chitobiose moiety protected with acid-labile TBDMS groups has been prepared. The building block was used in Fmoc solid-phase synthesis of a glycopeptide fragment corresponding to residues 447–460 of protein S which has a potential N-glycosylation site at Asn 458. The TBDMS groups of the chitobiose moiety were removed during cleavage of the glycopeptide from the solid phase, thus simplifying synthesis as compared to when using acetyl protection for the carbohydrate. Protein S is an anticoagulant which may be inactivated by complexation by C4b binding protein (C4BP). The protein S 447-460 glycopeptide was found to be a more efficient inhibitor of complex formation than the non-glycosylated parent peptide, indicating that protein S may carry an N-linked glycan at Asn 458.