科研之友
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摘要
The N-glycosylation of the model nematode Caenorhabditis elegans has proven to be highly variable and rather complex; it is an example to contradict the existing impression that "simple" organisms possess also a rather simple glycomic capacity. In previous studies in a number of laboratories, N-glycans with up to four fucose residues have been detected. However, although the linkage of three fucose residues to the N,N'-diacetylchitobiosyl core has been proven by structural and enzymatic analyses, the nature of the fourth fucose has remained uncertain. By constructing a triple mutant with deletions in the three genes responsible for core fucosylation (fut-1, fut-6 and fut-8), we have produced a nematode strain lacking products of these enzymes, but still retaining maximally one fucose residue on its N-glycans. Using mass spectrometry and HPLC in conjunction with chemical and enzymatic treatments as well as NMR, we examined a set of alpha-mannosidase-resistant N-glycans. Within this glycomic sub-pool, we can reveal that the core beta-mannose can be trisubstituted and so carries not only the ubiquitous alpha 1,3- and alpha 1,6-mannose residues, but also a "bisecting" alpha-galactose, which is substoichiometrically modified with fucose or methylfucose. In addition, the alpha 1,3-mannose can also be alpha-galactosylated. Our data, showing the presence of novel N-glycan modifications, will enable more targeted studies to understand the biological functions and interactions of nematode glycans.
- 出版日期2015-8
