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Title: Mutational analysis of endoxylanases XylA and XylB from the phytopathogen Fusarium graminearum reveals comprehensive insights into their inhibitor insensitivity
Authors: Beliën, Tim
Van Campenhout, Steven
Van Acker, Maarten
Courtin, Christophe M.
Delcour, Jan A.
VoIckaert, Guido
Issue Date: 2007
Abstract: Endo-beta-1,4-xylanases (EC; endoxylanases), key enzymes in the degradation of xylan, are considered to play an important role in phytopathogenesis, as they occupy a prominent position in the arsenal of hydrolytic enzymes secreted by phytopathogens to breach the cell wall and invade the plant tissue. Plant endoxylanase inhibitors are increasingly being pinpointed as part of a counterattack mechanism. To understand the surprising XIP-type endoxylanase inhibitor insensitivity of endoxylanases XylA and XylB from the phytopathogen Fusarium graminearum, an extensive mutational study of these enzymes was performed. Using combinatorial and site-directed mutagenesis, the XIP insensitivity of XylA as well as XylB was proven to be solely due to amino acid sequence adaptations in the "thumb" structural region. While XylB residues Cys(141), Asp(148), and CYS 149 were shown to prevent XIP interaction, the XIP insensitivity of XylA could be ascribed to the occurrence of only one aberrant residue, i.e., Val(151). This study, in addition to providing a thorough explanation for the XIP insensitivity of both F. graminearum endoxylanases at the molecular level, generated XylA and XylB mutants with altered inhibition specificities and pH optima. As this is the first experimental elucidation of the molecular determinants dictating the specificity of the interaction between endoxylanases of phytopathogenic origin and a plant inhibitor, this work sheds more light on the ongoing evolutionary arms race between plants and phytopathogenic fungi involving recognition of endoxylanases.
Notes: Katholieke Univ Leuven, Lab Food Chem & Biochem, B-3001 Louvain, Belgium. Katholieke Univ Leuven, Lab Gene Technol, B-3001 Louvain, Belgium. Univ Hasselt & Transnatl Univ Limburg, Biomed Res Inst, B-3590 Diepenbeek, Belgium.Belien, T, Katholieke Univ Leuven, Lab Food Chem & Biochem, Kasteelpk Arenberg 20, B-3001 Louvain, Belgium.tim.belien@biw.kuleuven.be
URI: http://hdl.handle.net/1942/4092
DOI: 10.1128/AEM.00442-07
ISI #: 000248197400025
ISSN: 0099-2240
Category: A1
Type: Journal Contribution
Validation: ecoom, 2008
Appears in Collections: Research publications

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