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1fh8

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[[Image:1fh8.jpg|left|200px]]
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{{STRUCTURE_1fh8| PDB=1fh8 | SCENE= }}
{{STRUCTURE_1fh8| PDB=1fh8 | SCENE= }}
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'''CRYSTAL STRUCTURE OF THE XYLANASE CEX WITH XYLOBIOSE-DERIVED ISOFAGOMINE INHIBITOR'''
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===CRYSTAL STRUCTURE OF THE XYLANASE CEX WITH XYLOBIOSE-DERIVED ISOFAGOMINE INHIBITOR===
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==Overview==
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Detailed insights into the mode of binding of a series of tight-binding aza-sugar glycosidase inhibitors of two fundamentally different classes are described through X-ray crystallographic studies of complexes with the retaining family 10 xylanase Cex from Cellulomonas fimi. Complexes with xylobiose-derived aza-sugar inhibitors of the substituted "amidine" class (xylobio-imidazole, K(i) = 150 nM; xylobio-lactam oxime, K(i) = 370 nM) reveal lateral interaction of the "glycosidic" nitrogen with the acid/base catalyst (Glu127) and hydrogen bonding of the sugar 2-hydroxyl with the catalytic nucleophile (Glu233), as expected. Tight binding of xylobio-isofagomine (K(i) = 130 nM) appears to be a consequence of strong interactions of the ring nitrogen with the catalytic nucleophile while, surprisingly, no direct protein contacts are made with the ring nitrogen of the xylobio-deoxynojirimycin analogue (K(i) = 5800 nM). Instead the nitrogen interacts with two ordered water molecules, thereby accounting for its relatively weaker binding, though it still binds some 1200-fold more tightly than does xylobiose, presumably as a consequence of electrostatic interactions at the active site. Dramatically weaker binding of these same inhibitors to the family 11 xylanase Bcx from Bacillus circulans (K(i) from 0.5 to 1.5 mM) is rationalized for the substituted amidines on the basis that this enzyme utilizes a syn protonation trajectory and likely hydrolyzes via a (2,5)B boat transition state. Weaker binding of the deoxynojirimycin and isofagomine analogues likely reflects the energetic penalty for distortion of these analogues to a (2,5)B conformation, possibly coupled with destabilizing interactions with Tyr69, a conserved, catalytically essential active site residue.
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{{ABSTRACT_PUBMED_10995222}}
==About this Structure==
==About this Structure==
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[[Category: Inhibitor]]
[[Category: Inhibitor]]
[[Category: Xylanase]]
[[Category: Xylanase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 16:19:20 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 03:14:30 2008''

Revision as of 00:14, 1 July 2008

Image:1fh8.png

Template:STRUCTURE 1fh8

CRYSTAL STRUCTURE OF THE XYLANASE CEX WITH XYLOBIOSE-DERIVED ISOFAGOMINE INHIBITOR

Template:ABSTRACT PUBMED 10995222

About this Structure

1FH8 is a Single protein structure of sequence from Cellulomonas fimi. Full crystallographic information is available from OCA.

Reference

Detailed structural analysis of glycosidase/inhibitor interactions: complexes of Cex from Cellulomonas fimi with xylobiose-derived aza-sugars., Notenboom V, Williams SJ, Hoos R, Withers SG, Rose DR, Biochemistry. 2000 Sep 26;39(38):11553-63. PMID:10995222

Page seeded by OCA on Tue Jul 1 03:14:30 2008

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