Investigation and correction of the gene-derived sequence of glutenin subunit 1Dx2 by matrix-assisted laser desorption/ionisation mass spectrometry

Direct matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) analysis of a mixture of tryptic peptides was used to verify the gene-derived amino acid sequence of the high molecular weight (HMW) subunit 1Dx2 of bread wheat. Analysis of the digest was performed by recording several MALDI mass spectra of the mixture at low, medium and high mass ranges, and optimising the matrix and the acquisition parameters for each mass range. This resulted in coverage of the whole sequence except for a short fragment T3 (3 amino acids), which was not detected. It also allowed the insertion of a Pro residue in position 59 to be identified. The results obtained provide evidence for the lack of a substantial level of glycosylation or other posttranslational modifications of subunit 1Dx2, and demonstrate that MALDI-MS is the most useful method presently available for the direct verification of the gene-derived sequences of HMW glutenin subunits and similar proteins.