Oligosaccharide binding to family 11 xylanases: both covalent intermediate and mutant product complexes display (2,5)B conformations at the active centre.
The glycoside hydrolase sequence-based classification reveals two families of enzymes which hydrolyse the beta-1,4-linked backbone of xylan, xylanases, termed families GH-10 and GH-11. Family GH-11 xylanases are intriguing in that catalysis is performed via a covalent intermediate adopting an unusual (2,5)B (boat) conformation, a conformation which also fulfils the stereochemical constraints of the oxocarbenium ion-like transition state. Here, the 1.9 A structure of a nucleophile, E94A, mutant of the Xyn11 from Bacillus agaradhaerens in complex with xylotriose is presented. Intriguingly, this complex also adopts the (2,5)B conformation in the -1 subsite, with the vacant space provided by the Glu-->Ala mutation allowing the sugar to adopt the alpha-configuration at C1. The structure of the covalent 2-deoxy-2-fluoroxylobiosyl-enzyme intermediate has been extended to atomic (1.1 A) resolution.
Sabini
E
E
Department of Chemistry, Structural Biology Laboratory, University of York, Heslington, York YO10 5DD, England.
Wilson
K S
KS
Danielsen
S
S
Schülein
M
M
Davies
G J
GJ
D019943:Amino Acid Substitution; D001407:Bacillus / Q000201:enzymology*; D003460:Crystallization; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009154:Mutation; D009844:Oligosaccharides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D043325:Xylan Endo-1,3-beta-Xylosidase; D014990:Xylans / Q000737:chemistry; D014995:Xylosidases / Q000737:chemistry* / Q000235:genetics
D009844:Oligosaccharides; D014990:Xylans; C074758:2-(trimethylsilyl)ethyl O-(2,3-di-O-benzylxylopyranosyl)(1-4)-O-(2,3-di-O-benzoylxylopyranosyl)-(1-4)-O-(2,3-di-O-benzylxylopyranosyl)-(1-4)-2,3-di-O-benzoylxylopyranoside; D014995:Xylosidases; D043325:Xylan Endo-1,3-beta-Xylosidase