alpha2,3/alpha2,6-Sialylation of N-glycans: non-synonymous signals with marked developmental regulation in bovine reproductive tracts.
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.
Siebert
Hans-Christian
HC
Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig-Maximilians-University, Veterinärstr. 13, 80539 München, Germany.
Rosen
Jimmy
J
Seyrek
Kamil
K
Kaltner
Herbert
H
André
Sabine
S
Bovin
Nicolai V
NV
Nyholm
Per-Georg
PG
Sinowatz
Fred
F
Gabius
Hans-Joachim
HJ
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
D004187:Disaccharides; D037102:Lectins; D009844:Oligosaccharides; D011134:Polysaccharides; D012799:Sialyltransferases; D019158:N-Acetylneuraminic Acid; D005690:Galactose; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase