The maize β-glucosidase isoenzymes ZMGlu1 and ZMGlu2 hydrolyse the abundant natural substrate DIMBOAGlc (2-O-β-d-glucopyranosyl-4-hydroxy-7-methoxy-1,4-benzoxazin-3-one), whose aglycone DIMBOA (2,4-hydroxy-7-methoxy-1,4-benzoxazin-3-one) is the major defence chemical protecting seedlings and young plant parts against herbivores and other pests. The two isoenzymes hydrolyse DIMBOAGlc with similar kinetics but differ from each other and their sorghum homologues with respect to specificity towards other substrates. To gain insights into the mechanism of substrate (i.e. aglycone) specificity between the two maize isoenzymes and their sorghum homologues, ZMGlu1 was produced in Escherichia coli, purified, crystallized and its structure solved at 2.5 Å resolution by X-ray crystallography. In addition, the complex of ZMGlu1 with the non-hydrolysable inhibitor p-nitrophenyl β-d-thioglucoside was crystallized and, based on the partial electron density, a model for the inhibitor molecule within the active site is proposed. The inhibitor is located in a slot-like active site where its aromatic aglycone is held by stacking interactions with Trp-378. Whereas some of the atoms on the non-reducing end of the glucose moiety can be modelled on the basis of the electron density, most of the inhibitor atoms are highly disordered. This is attributed to the requirement of the enzyme to accommodate two different species, namely the substrate in its ground state and in its distorted conformation, for catalysis.
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February 2001
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Research Article|
February 08 2001
Crystal structure of a monocotyledon (maize ZMGlu1) β-glucosidase and a model of its complex with p-nitrophenyl β-d-thioglucoside
Mirjam CZJZEK;
Mirjam CZJZEK
1
*Architecture et Fonction des Macromolecules Biologiques–AFMB-UMR 6098, CNRS and Universités d'Aix-Marseille I et II, 31 Chemin Joseph Aiguier, F13402 Marseille Cedex 20, France
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Muzaffer CICEK;
Muzaffer CICEK
†Department of Biology, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, U.S.A.
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Véronique ZAMBONI;
Véronique ZAMBONI
*Architecture et Fonction des Macromolecules Biologiques–AFMB-UMR 6098, CNRS and Universités d'Aix-Marseille I et II, 31 Chemin Joseph Aiguier, F13402 Marseille Cedex 20, France
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Wim P. BURMEISTER;
Wim P. BURMEISTER
‡European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
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David R. BEVAN;
David R. BEVAN
§Department of Biochemistry, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, U.S.A.
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Bernard HENRISSAT;
Bernard HENRISSAT
*Architecture et Fonction des Macromolecules Biologiques–AFMB-UMR 6098, CNRS and Universités d'Aix-Marseille I et II, 31 Chemin Joseph Aiguier, F13402 Marseille Cedex 20, France
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Asim ESEN
Asim ESEN
*Architecture et Fonction des Macromolecules Biologiques–AFMB-UMR 6098, CNRS and Universités d'Aix-Marseille I et II, 31 Chemin Joseph Aiguier, F13402 Marseille Cedex 20, France
§Department of Biochemistry, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, U.S.A.
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Publisher: Portland Press Ltd
Received:
June 16 2000
Revision Received:
November 06 2000
Accepted:
December 01 2000
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 2001
2001
Biochem J (2001) 354 (1): 37–46.
Article history
Received:
June 16 2000
Revision Received:
November 06 2000
Accepted:
December 01 2000
Citation
Mirjam CZJZEK, Muzaffer CICEK, Véronique ZAMBONI, Wim P. BURMEISTER, David R. BEVAN, Bernard HENRISSAT, Asim ESEN; Crystal structure of a monocotyledon (maize ZMGlu1) β-glucosidase and a model of its complex with p-nitrophenyl β-d-thioglucoside. Biochem J 15 February 2001; 354 (1): 37–46. doi: https://doi.org/10.1042/bj3540037
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