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LIMITED ADDITION OF THE 6-ARM Β1,2-LINKED N-ACETYLGLUCOSAMINE (GLCNAC) RESIDUE FACILITATES THE FORMATION OF THE LARGEST N-GLYCAN IN PLANTS
(Pub Med, 2015-07-03) Jae, Yong Yoo; Ki, Seong Ko; Hyun-Kyeong, Seo; Seongha, Park; Wahyu, Indra Duwi Fanata; Rikno, Harmoko; Nirmal Kumar, Ramasamy; Thiyagarajan, Thulasinathan; Tesfaye, Mengiste; Jae-Min, Lim; Sang, Yeol Lee; Kyun, Oh Lee
The most abundant N-glycan in plants is the paucimannosidic N-glycan with core β1,2-xylose and α1,3-fucose residues (Man3XylFuc(GlcNAc)2). Here, we report a mechanism in Arabidopsis thaliana that efficiently produces the largest N-glycan in plants. Genetic and biochemical evidence indicates that the addition of the 6-arm β1,2-GlcNAc residue by N-acetylglucosaminyltransferase II (GnTII) is less effective than additions of the core β1,2-xylose and α1,3-fucose residues by XylT, FucTA, and FucTB in Arabidopsis. Furthermore, analysis of gnt2 mutant and 35S:GnTII transgenic plants shows that the addition of the 6-arm non-reducing GlcNAc residue to the common N-glycan acceptor GlcNAcMan3(GlcNAc)2 inhibits additions of the core β1,2-xylose and α1,3-fucose residues. Our findings indicate that plants limit the rate of the addition of the 6-arm GlcNAc residue to the common N-glycan acceptor as a mechanism to facilitate formation of the prevalent N-glycans with Man3XylFuc(GlcNAc)2 and (GlcNAc)2Man3XylFuc(GlcNAc)2 structures.