Structural basis for inhibition of Aspergillus niger xylanase by triticum aestivum xylanase inhibitor-I.
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.
Sansen
Stefaan
S
Laboratory of Analytical Chemistry and Medicinal Physicochemistry, Katholieke Universiteit Leuven, E. van Evenstraat 4, B-3000 Leuven, Belgium.
De Ranter
Camiel J
CJ
Gebruers
Kurt
K
Brijs
Kristof
K
Courtin
Christophe M
CM
Delcour
Jan A
JA
Rabijns
Anja
A
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*
D004791:Enzyme Inhibitors; D010940:Plant Proteins; C422246:TAXI I protein, Triticum aestivum; D014995:Xylosidases