Atomic (0.94 A) resolution structure of an inverting glycosidase in complex with substrate.
The crystal structure of Clostridium thermocellum endoglucanase CelA in complex with cellopentaose has been determined at 0.94 A resolution. The oligosaccharide occupies six D-glucosyl-binding subsites, three on either side of the scissile glycosidic linkage. The substrate and product of the reaction occupy different positions at the reducing end of the cleft, where an extended array of hydrogen-bonding interactions with water molecules fosters the departure of the leaving group. Severe torsional strain upon the bound substrate forces a distorted boat(2,5) B conformation for the glucosyl residue bound at subsite -1, which facilitates the formation of an oxocarbenium ion intermediate and might favor the breakage of the sugar ring concomitant with catalysis.
Guérin
Diego M A
DM
Unité de Biochimie Structurale, CNRS URA 2185, Institut Pasteur, 25 rue du Dr. Roux, 75724 Paris cédex 15, France.
Lascombe
Marie-Bernard
MB
Costabel
Marcelo
M
Souchon
Hélène
H
Lamzin
Victor
V
Béguin
Pierre
P
Alzari
Pedro M
PM
D001665:Binding Sites; D002480:Cellulase / Q000737:chemistry* / Q000378:metabolism*; D003013:Clostridium / Q000201:enzymology*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008024:Ligands; D008958:Models, Molecular; D009844:Oligosaccharides / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D014867:Water / Q000378:metabolism
D008024:Ligands; D009844:Oligosaccharides; D014867:Water; C019193:maltopentaose; C074775:CelA endoglucanase; D002480:Cellulase