Characterization of the cell wall glycoproteome of tomato (Solanum lycopersicum) fruit by tandem mass spectrometry

摘要

A total of 232 glycoproteins were identified from both the high salt and low salt fractions. More than 75percent of these were predicted to contain a signal peptide targeting them for secretion to the cell wall and other extra cellular spaces. More than 90percent of the proteins identified were predicted to contain N-glycosylation sequence motifs. A functional analysis of the proteins identified suggest activities that are, for the most part, consistent with a cell wall location. The analysis of a single fraction (RT 19 min) by PI-IDA on a 4000 QTrap has allowed the identification of 64 distinct glycopeptides from 33proteins. The glycosylation sites and glycan composition for 28 of the glycopeptides were determined by manual inspection of the MS/MS spectra, A sub set of these were verified by PID analysis on a Synapt HDMS and through PNGase A digestion. 11 glycopeptides were detected with 2 or more glycan isoforms and four proteins were detected with multiple glycopeptides. The glycan compositions for majority of the glycopeptides consisted of masses at 1008.4 Da velence [(Hex)_(2) (HexNAc)_(2) (Deoxyhexose)_(1) (Pent)_(1)]; 1170.5 Da velence [(Hex)_(3) (HexNAc)_(2) (Deoxyhexose)_(1) (Pent)_(1)] and 1024.4 Da velence [(Hex)_(3) (HexNAc)_(2) (Pent)_(1)].