Title: His374 of wheat endoxylanase inhibitor TAXI-I stabilizes complex formation with glycoside hydrolase family 11 endoxylanases
Authors: Fierens, Katleen
Gils, Ann
Sansen, Stefaan
Brijs, Kristof
Courtin, Christophe
Declerck, Paul
De Ranter, Camiel
Gebruers, Kurt
Rabijns, Anja
Robben, Johan
Campenhout, Steven
Volckaert, Guido
Delcour, Jan # ×
Issue Date: Nov-2005
Publisher: Published by Blackwell Pub. on behalf of the Federation of European Biochemical Societies
Series Title: FEBS Journal vol:272 issue:22 pages:5872-5882
Abstract: Wheat endoxylanase inhibitor TAXI-I inhibits microbial glycoside hydrolase family 11 endoxylanases. Crystallographic data of an Aspergillus niger endoxylanase-TAXI-I complex showed His374 of TAXI-I to be a key residue in endoxylanase inhibition. Its role in enzyme-inhibitor interaction was further investigated by site-directed mutagenesis of His374 into alanine, glutamine or lysine. Binding kinetics and affinities of the molecular interactions between A. niger, Bacillus subtilis, Trichoderma longibrachiatumendoxylanases and wild-type TAXI-I and TAXI-I His374 mutants were determined by surface plasmon resonance analysis. Enzyme-inhibitor binding was in accordance with a simple 1 : 1 binding model. Association and dissociation rate constants of wild-type TAXI-I towards the endoxylanases were in the range between 1.96 and 36.1 x 10(4)m(-1) x s(-1) and 0.72-3.60 x 10(-4) x s(-1), respectively, resulting in equilibrium dissociation constants in the low nanomolar range. Mutation of TAXI-I His374 to a variable degree reduced the inhibition capacity of the inhibitor mainly due to higher complex dissociation rate constants (three- to 80-fold increase). The association rate constants were affected to a smaller extent (up to eightfold decrease). Substitution of TAXI-I His374 therefore strongly affects the affinity of the inhibitor for the enzymes. In addition, the results show that His374 plays a critical role in the stabilization of the endoxylanase-TAXI-I complex rather than in the docking of inhibitor onto enzyme.
ISSN: 1742-464X
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Centre for Food and Microbial Technology
Laboratory for Pharmaceutical Biology (-)
Division of Gene Technology (-)
Biochemistry, Molecular and Structural Biology Section
Administration Rectorial Services - miscellaneous
× corresponding author
# (joint) last author

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