Comparative study of carbohydrate chains released from the oviducal mucins of the two very closely related amphibian species Bombina bombina and Bombina variegata.
The eggs of amphibians are surrounded by an extracellular matrix, termed jelly coat, which is mainly composed of hydrated mucin-type glycoproteins. These highly glycosylated molecules are synthesized by the oviduct and play an important role in the fertilization process. From a structural and chemical point of view, these oviducal mucins are very different from one species to another and they could be involved in the species-specificity of gamete interactions or could influence the parasite tropism. Bombina bombina and Bombina variegata are the two most closely related species within the genus, which hybridize readily in nature. Divergence occurred during geographic isolation estimated at 2-7 million years ago. The oviducal mucins of these species have been studied at the carbohydrate level, and the primary structures of 28 compounds have been established by NMR spectroscopy. The carbohydrate chains released from the oviducal mucins of the two species were similar and characterized by the common sequences GlcNAc(beta 1-3)[Fuc(alpha 1-4)]GlcNAc(beta 1-6) and GlcNAc(alpha 1-4)Gal(beta 1-4)Gal(beta 1-3) attached to GalNAc-ol (core 2). Nevertheless, some differences confirmed the strict species-specificity of amphibian oviducal carbohydrate chains observed previously. On the one hand, the presence of beta Gal 1,4-linked to beta GlcNAc in B. bombina, but not in B. variegata, can indicate that beta 4GalT: beta GlcNAc and beta 4GalT: beta Gal are two distinct glycosyltransferases. On the other hand, deaminoneuraminic acid (Kdn) is present in B. bombina, and N -glycolylneuraminic acid (NeuGc) in B. variegata. Although the enzymes involved in the biosynthesis of Kdn are not as well characterized, it can be suggested that at least one step of the biosynthetic pathway of NeuAc has been disrupted, leading the B. bombina oviducal NeuAc-9-synthase to use Man-6-P as a substrate, instead of ManNAc-6-P.
Coppin
Alexandra
A
Unité de Glycobiologie Structurale et Fonctionnelle, UMR 8576 du CNRS, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq cedex, France.
Florea
Doina
D
Maes
Emmanuel
E
Cogálniceanu
Dan
D
Strecker
Gérard
G
D000663:Amphibians / Q000378:metabolism*; D000818:Animals; D002240:Carbohydrate Sequence; D005260:Female; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008969:Molecular Sequence Data; D009077:Mucins / Q000737:chemistry / Q000378:metabolism; D019158:N-Acetylneuraminic Acid / Q000737:chemistry; D009844:Oligosaccharides / Q000737:chemistry* / Q000302:isolation & purification; D010057:Oviducts / Q000737:chemistry / Q000378:metabolism*; D013045:Species Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013402:Sugar Alcohols / Q000737:chemistry
D009077:Mucins; D009844:Oligosaccharides; D013402:Sugar Alcohols; D019158:N-Acetylneuraminic Acid