N-glycans of Phaeodactylum tricornutum diatom and functional characterization of its N-acetylglucosaminyltransferase I enzyme |
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Authors: | Baïet Bérengère Burel Carole Saint-Jean Bruno Louvet Romain Menu-Bouaouiche Laurence Kiefer-Meyer Marie-Christine Mathieu-Rivet Elodie Lefebvre Thomas Castel Hélène Carlier Aude Cadoret Jean-Paul Lerouge Patrice Bardor Muriel |
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Institution: | Université de Rouen, Laboratoire Glycobiologie et Matrice Extracellulaire Végétale, Faculté des Sciences, 76821 Mont-Saint-Aignan Cédex, France. |
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Abstract: | N-glycosylation, a major co- and post-translational event in the synthesis of proteins in eukaryotes, is unknown in aquatic photosynthetic microalgae. In this paper, we describe the N-glycosylation pathway in the diatom Phaeodactylum tricornutum. Bio-informatic analysis of its genome revealed the presence of a complete set of sequences potentially encoding for proteins involved in the synthesis of the lipid-linked Glc(3)Man(9)GlcNAc(2)-PP-dolichol N-glycan, some subunits of the oligosaccharyltransferase complex, as well as endoplasmic reticulum glucosidases and chaperones required for protein quality control and, finally, the α-mannosidase I involved in the trimming of the N-glycan precursor into Man-5 N-glycan. Moreover, one N-acetylglucosaminyltransferase I, a Golgi glycosyltransferase that initiates the synthesis of complex type N-glycans, was predicted in the P. tricornutum genome. We demonstrated that this gene encodes for an active N-acetylglucosaminyltransferase I, which is able to restore complex type N-glycans maturation in the Chinese hamster ovary Lec1 mutant, defective in its endogeneous N-acetylglucosaminyltransferase I. Consistent with these data, the structural analyses of N-linked glycans demonstrated that P. tricornutum proteins carry mainly high mannose type N-glycans ranging from Man-5 to Man-9. Although representing a minor glycan population, paucimannose N-glycans were also detected, suggesting the occurrence of an N-acetylglucosaminyltransferase I-dependent maturation of N-glycans in this diatom. |
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Keywords: | Carbohydrate Biosynthesis Carbohydrate Structure Glycosylation Golgi Plant N-Acetylglucosaminyltransferase Phaeodactylum Diatom Glycosyltransferase Microalgae |
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