Structural and Functional Characterization of a Constrained Asx-Turn Motif

The specific and timely glycosylation of proteins is associated with the proper structure, function, and targeting of glycoprotein conjugates. For N-linked glycosylation, catalyzed by the enzyme oligosaccharyl transferase (OT), we have recently proposed that the fidelity of this modification may be associated with particular conformational tendencies of polypeptide substrates which contain the consensus sequence Asn-Xaa-Thr/Ser. The presence of a local Asx-turn ,about the Asn-Xaa-Thr/Ser sequence, is central to this proposal, which was based on studies of the glycosyl acceptor properties of linear and cyclic peptides. Herein, we describe a new substrate for N-linked glycosylation which is conformationally constrained to adopt an Asx-turn and specifically designed to test this proposal