PubMed:14760718 JSONTXT

{"project":"Lectin_function","denotations":[{"id":"T1","span":{"begin":812,"end":818},"obj":"GX_000027"},{"id":"T2","span":{"begin":812,"end":818},"obj":"GX_000045"},{"id":"T3","span":{"begin":955,"end":961},"obj":"GX_000027"},{"id":"T4","span":{"begin":955,"end":961},"obj":"GX_000045"},{"id":"T5","span":{"begin":1180,"end":1187},"obj":"GX_000027"},{"id":"T6","span":{"begin":1180,"end":1187},"obj":"GX_000045"},{"id":"T7","span":{"begin":1208,"end":1229},"obj":"GX_000069"}],"text":"Screening for N-glycosylated proteins by liquid chromatography mass spectrometry.\nIn the last few years mass spectrometry has become the method of choice for characterization of post-translationally modified proteins. Whereas most protein chemical modifications are binary in the sense that only one change can be associated with a given residue, many different oligosaccharides can be attached to a glycosylation site residue. The detailed characterization of glycoproteins in complex biological samples is extremely challenging. However, information on N-glycosylation can be gained at an intermediary level. Here we demonstrate a procedure for mapping N-glycosylation sites in complex mixtures by reducing sample complexity and enriching glycoprotein content. Glycosylated proteins are selected by an initial lectin chromatography step and digested with endoproteinase Lys-C. Glycosylated peptides are then selected from the digest mixture by a second lectin chromatography step. The glycan components are removed with N-glycosidase F and the peptides digested with trypsin before analysis by on-line reversed-phase liquid chromatography mass spectrometry. Using two different lectins, concanavalin A and wheat germ agglutinin, this procedure was applied to human serum and a total of 86 N-glycosylation sites in 77 proteins were identified."}