title: alpha2,3/alpha2,6-Sialylation of N-glycans: non-synonymous signals with marked developmental regulation in bovine reproductive tracts.
abstract: The glycan part endows cellular glycoconjugates with significant potential for biological recognition. N-Glycan branches often end with alpha2,3/alpha2,6-sialylation, posing the question whether and how placement of the sialic acid at 3 - or 6 -acceptor positions of galactose has cell biological relevance. As attractive model to study developmental regulation we monitored the expression of alpha2,3/alpha2,6-sialylated determinants in fetal and adult bovine testes and ovaries by lectin histochemistry. Distinct expression patterns were detected in both organ types. Oocyte staining, as a prominent example, was restricted to the presence of alpha2,6-sialylated glycans. Treatment with sialidase abolished binding and thus excluded sulfate esters as lectin targets. We added computer simulations to rationalize the observed evidence for non-random expression of the two closely related sialylgalactose isomers. Extensive molecular mechanics and molecular dynamics calculations reveal that the seemingly minor shift of the glycosidic bond from the alpha2,3 position to the alpha2,6 configuration causes significant shape and flexibility changes. They give each disaccharide its own characteristic meaning as signal in the sugar code.
authors.affiliation: Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig-Maximilians-University, Veterinärstr. 13, 80539 München, Germany.
authors.forename: Hans-Christian
authors.initials: HC
authors.lastname: Siebert
authors.forename: Jimmy
authors.initials: J
authors.lastname: Rosen
authors.forename: Kamil
authors.initials: K
authors.lastname: Seyrek
authors.forename: Herbert
authors.initials: H
authors.lastname: Kaltner
authors.forename: Sabine
authors.initials: S
authors.lastname: André
authors.forename: Nicolai V
authors.initials: NV
authors.lastname: Bovin
authors.forename: Per-Georg
authors.initials: PG
authors.lastname: Nyholm
authors.forename: Fred
authors.initials: F
authors.lastname: Sinowatz
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Gabius
mesh_terms: D000818:Animals; D002236:Carbohydrate Conformation; D002417:Cattle; D003198:Computer Simulation; D004187:Disaccharides / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D005260:Female; D005690:Galactose / Q000737:chemistry; D006031:Glycosylation; D037102:Lectins / Q000032:analysis / Q000378:metabolism; D008297:Male; D008958:Models, Molecular; D015394:Molecular Structure; D019158:N-Acetylneuraminic Acid / Q000737:chemistry*; D009844:Oligosaccharides / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D010053:Ovary / Q000737:chemistry* / Q000196:embryology / Q000254:growth & development; D011134:Polysaccharides / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D012799:Sialyltransferases / Q000378:metabolism; D013737:Testis / Q000737:chemistry* / Q000196:embryology / Q000254:growth & development; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
chemical_list: D004187:Disaccharides; D037102:Lectins; D009844:Oligosaccharides; D011134:Polysaccharides; D012799:Sialyltransferases; D019158:N-Acetylneuraminic Acid; D005690:Galactose; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase