The current invention provides polypeptides and polypeptide conjugates that include an exogenous N-linked
glycosylation sequence. The N-linked
glycosylation sequence is preferably a substrate for an oligosaccharyltransferase (e.g., bacterial PgIB), which can catalyze the transfer of a
glycosyl moiety from a lipid-bound
glycosyl donor molecule (e.g., a lipid-
pyrophosphate-linked
glycosyl moiety) to an
asparagine (N) residue of the
glycosylation sequence. In one example, the
asparagine residue is part of an exogenous N-linked glycosylation sequence of the invention. The invention further provides methods of making the polypeptide conjugates that include contacting a polypeptide having an N-linked glycosylation sequence of the invention and a lipid-
pyrophosphate-linked glycosyl
moiety (or
phospholipid-linked glycosyl moiety) in the presence of an oligosaccharyltransferase under conditions sufficient for the
enzyme to transfer the glycosyl moiety to an
asparagine residue of the N-linked glycosylation sequence. Exemplary glycosyl moieties that can be conjugated to the glycosylation sequence include GlcNAc, GlcNH, bacillosamine, 6-hydroybacillosamine, GalNAc, GaINH, GlcNAc-GlcNAc, GlcNAc-GlcNH, GlcNAc-Gal, GlcNAc-GlcNAc-Gal-Sia, GlcNAc-Gal-Sia, GlcNAc-GlcNAc-Man, and GlcNAc-GlcNAc-Man(Man)2. The transferred glycosyl moiety is optionally modified with a modifying group, such as a
polymer (e.g., PEG). In one example, the modified glycosyl moiety is a GIcNAc or a
sialic acid moiety.