title: Structural basis for inhibition of Aspergillus niger xylanase by triticum aestivum xylanase inhibitor-I.
abstract: Plants developed a diverse battery of defense mechanisms in response to continual challenges by a broad spectrum of pathogenic microorganisms. Their defense arsenal includes inhibitors of cell wall-degrading enzymes, which hinder a possible invasion and colonization by antagonists. The structure of Triticum aestivum xylanase inhibitor-I (TAXI-I), a first member of potent TAXI-type inhibitors of fungal and bacterial family 11 xylanases, has been determined to 1.7-A resolution. Surprisingly, TAXI-I displays structural homology with the pepsin-like family of aspartic proteases but is proteolytically nonfunctional, because one or more residues of the essential catalytical triad are absent. The structure of the TAXI-I. Aspergillus niger xylanase I complex, at a resolution of 1.8 A, illustrates the ability of tight binding and inhibition with subnanomolar affinity and indicates the importance of the C-terminal end for the differences in xylanase specificity among different TAXI-type inhibitors.
authors.affiliation: Laboratory of Analytical Chemistry and Medicinal Physicochemistry, Katholieke Universiteit Leuven, E. van Evenstraat 4, B-3000 Leuven, Belgium.
authors.forename: Stefaan
authors.initials: S
authors.lastname: Sansen
authors.forename: Camiel J
authors.initials: CJ
authors.lastname: De Ranter
authors.forename: Kurt
authors.initials: K
authors.lastname: Gebruers
authors.forename: Kristof
authors.initials: K
authors.lastname: Brijs
authors.forename: Christophe M
authors.initials: CM
authors.lastname: Courtin
authors.forename: Jan A
authors.initials: JA
authors.lastname: Delcour
authors.forename: Anja
authors.initials: A
authors.lastname: Rabijns
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology*; D001665:Binding Sites; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism; D015394:Molecular Structure; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014995:Xylosidases / Q000037:antagonists & inhibitors / Q000737:chemistry*
chemical_list: D004791:Enzyme Inhibitors; D010940:Plant Proteins; C422246:TAXI I protein, Triticum aestivum; D014995:Xylosidases