Isolation and characterization of major glycoproteins of pigeon egg white - Ubiquitous presence of unique N-glycans containing Gal alpha 1-4Gal

Ovotransferrin (POT), two ovalbumins (POA(hi) and POA(lo)), and ovomucoid ( POM) were isolated from pigeon egg white (PEW). Unlike their chicken egg wh ite counterparts, PEW glycoproteins contain terminal Gal alpha1-4Gal, as ev idenced by GS-I lectin (specific for terminal alpha -Gal), anti-P-1 (Gal al pha1-4Gal beta1- 4GlcNAc beta1-3Gal beta1-4Glc beta1-1Cer) monoclonal antib ody, and P fimbriae on uropathogenic Escherichia coli (specific for Gal alp ha1-4Gal). Gal alpha1-4Gal on PEW glycoproteins were found in N-glycans rel easable by treatment with glycoamidase F. The respective contents of N-glyc ans in each glycoprotein were 3.5%, POT; 17%, POA(hi); and 31-37%, POM. POA (hi) has four N-glycosylation sites, in contrast to chicken ovalbumin, whic h has only one. High performance liquid chromatography analysis showed that N-glycans on POA(hi) were highly heterogeneous. Mass spectrometric analysi s revealed that the major N-glycans were monosialylated tri-, tetra-, and p enta-antennary oligosaccharides containing terminal Gal alpha1-4Gal with or without bisecting N-acetylglucosamine, Oligo saccharide chains terminating in Gal alpha1-4Gal are rare among N-glycans from the mammals and avians th at have been studied, and our finding is the first predominant presence of (Gal alpha1-4Gal)-terminated N-glycans.