title: Human insulin-like growth factor binding protein-6 is O-glycosylated.
abstract: Insulin-like growth factor binding protein-6 is abundant in cerebrospinal fluid and has a marked preferential binding affinity for IGF-II over IGF-I. The present study demonstrates that IGFBP-6 is O-glycosylated but not N-glycosylated. Carbohydrate analysis revealed the presence of approximately 20-30 carbohydrate residues/molecule. Galactosamine, galactose and sialic acid were most abundant, with glucosamine and fucose present in lower concentrations. Mannose was not detected. Enzymatic deglycosylation did not alter the high affinity of IGF binding protein-6 for IGF-II (Ka 4.4 +/- 2.2 x 10(11) M-1) or its preference for IGF-II over IGF-I. Glycosylation of IGFBP-6 may affect its secretion, in vivo stability or localization, but does not affect its ligand binding properties.
authors.affiliation: Growth and Development Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
authors.forename: L A
authors.initials: LA
authors.lastname: Bach
authors.forename: N R
authors.initials: NR
authors.lastname: Thotakura
authors.forename: M M
authors.initials: MM
authors.lastname: Rechler
mesh_terms: D002241:Carbohydrates / Q000032:analysis; D002352:Carrier Proteins / Q000134:cerebrospinal fluid / Q000737:chemistry* / Q000378:metabolism; D006026:Glycoside Hydrolases; D006031:Glycosylation; D006801:Humans; D018976:Insulin-Like Growth Factor Binding Protein 6; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D037102:Lectins; D008970:Molecular Weight
chemical_list: D002241:Carbohydrates; D002352:Carrier Proteins; D018976:Insulin-Like Growth Factor Binding Protein 6; D037102:Lectins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D006026:Glycoside Hydrolases