title: Improved identification of wheat gluten proteins through alkylation of cysteine residues and peptide-based mass spectrometry.
abstract: The concentration and composition of wheat gluten proteins and the presence, concentration and location of cysteine residues therein are important for wheat flour quality. However, it is difficult to identify gluten proteins, as they are an extremely polymorphic mixture of prolamins. We here present methods for cysteine labeling of wheat prolamins with 4-vinylpyridine (4-VP) and iodoacetamide (IDAM) which, as compared to label-free analysis, substantially improve identification of cysteine-containing peptides in enzymic prolamin digests by electrospray ionization--tandem mass spectrometry. Both chymotrypsin and thermolysin yielded cysteine-containing peptides from different gluten proteins, but more proteins could be identified after chymotryptic digestion. In addition, to the best of our knowledge, we were the first to label prolamins with isotope coded affinity tags (ICAT), which are commonly used for quantitative proteomics. However, more peptides were detected after labeling gluten proteins with 4-VP and IDAM than with ICAT.
authors.affiliation: German Research Center for Food Chemistry, Leibniz Institute, Lise-Meitner-Strasse 34, D-85354 Freising, Germany. ine.rombouts@biw.kuleuven.be
authors.forename: Ine
authors.initials: I
authors.lastname: Rombouts
authors.forename: Bert
authors.initials: B
authors.lastname: Lagrain
authors.forename: Markus
authors.initials: M
authors.lastname: Brunnbauer
authors.forename: Jan A
authors.initials: JA
authors.lastname: Delcour
authors.forename: Peter
authors.initials: P
authors.lastname: Koehler
mesh_terms: D000478:Alkylation; D002918:Chymotrypsin / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry*; D005983:Glutens / Q000737:chemistry*; D013058:Mass Spectrometry; D010455:Peptides / Q000737:chemistry*; D055315:Prolamins / Q000737:chemistry; D040901:Proteomics; D013194:Staining and Labeling; D014908:Triticum / Q000737:chemistry*
chemical_list: D010455:Peptides; D055315:Prolamins; D005983:Glutens; D002918:Chymotrypsin; D003545:Cysteine