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Glycobiology. 2007 Aug;17(8):868-76. Epub 2007 May 9.

NetCGlyc 1.0: prediction of mammalian C-mannosylation sites.

Author information

1
Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77 Stockholm, Sweden. karin.julenius@sbc.su.se

Abstract

C-mannosylation is the attachment of an alpha-mannopyranose to a tryptophan via a C-C linkage. The sequence WXXW, in which the first Trp becomes mannosylated, has been suggested as a consensus motif for the modification, but only two-thirds of known sites follow this rule. We have gathered a data set of 69 experimentally verified C-mannosylation sites from the literature. We analyzed these for sequence context and found that apart from Trp in position +3, Cys is accepted in the same position. We also find a clear preference in position +1, where a small and/or polar residue (Ser, Ala, Gly, and Thr) is preferred and a Phe or a Leu residue discriminated against. The Protein Data Bank was searched for structural information, and five structures of C-mannosylated proteins were obtained. We showed that modified tryptophan residues are at least partly solvent exposed. A method predicting the location of C-mannosylation sites in proteins was developed using a neural network approach. The best overall network used a 21-residue sequence input window and information on the presence/absence of the WXXW motif. NetCGlyc 1.0 correctly predicts 93% of both positive and negative C-mannosylation sites. This is a significant improvement over the WXXW consensus motif itself, which only identifies 67% of positive sites. NetCGlyc 1.0 is available at http://www.cbs.dtu.dk/services/NetCGlyc/. Using NetCGlyc 1.0, we scanned the human genome and found 2573 exported or transmembrane transcripts with at least one predicted C-mannosylation site.

PMID:
17494086
DOI:
10.1093/glycob/cwm050
[Indexed for MEDLINE]

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