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Variability of polymorphic families of three types of xylanase inhibitors in the wheat grain proteome
Author(s) -
Croes Evi,
Gebruers Kurt,
Robben Johan,
Noben JeanPaul,
Samyn Bart,
Debyser Griet,
Van Beeumen Jozef,
Delcour Jan A.,
Courtin Christophe M.
Publication year - 2008
Publication title -
proteomics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.26
H-Index - 167
eISSN - 1615-9861
pISSN - 1615-9853
DOI - 10.1002/pmic.200700813
Subject(s) - xylanase , biology , proteome , glycoside hydrolase , glycosylation , biochemistry , molecular mass , enzyme
Cereals contain proteinaceous inhibitors of endo‐β‐1,4‐xylanases (E.C.3.2.1.8, xylanases). Since these xylanase inhibitors (XIs) are only active against xylanases of microbial origin and do not interact with plant endogenous xylanases, they are believed to act as a defensive barrier against phytopathogenic attack. So far, three types of XIs have been identified, i.e. Triticum aestivum XI (TAXI), xylanase inhibiting protein (XIP), and thaumatin‐like XI (TLXI) proteins. In this study the variation in XI forms present in wheat grain was elucidated using high‐resolution 2‐DE in combination with LC‐ESI‐MS/MS and biochemical techniques. Reproducible 2‐DE fingerprints of TAXI‐, XIP‐, and TLXI‐type XIs, selectively purified from whole meal of three European wheat cultivars using cation exchange chromatography followed by affinity chromatography, were obtained using a pH‐gradient of 6 to 11 and a molecular mass range of 10 to 60 kDa. Large polymorphic XI families, not known to date, which exhibit different p I ‐ and/or molecular mass values, were visualised by colloidal CBB staining. Identification of distinct genetic variants by MS/MS‐analysis provides a partial explanation for the observed XI heterogeneity. Besides genetic diversity, PTMs, such as glycosylation, account for the additional complexity of the 2‐DE patterns.