1QW8: Crystal Structure Of A Family 51 Alpha-L- Arabinofuranosidase In Complex With Ara-Alpha(1,3)-Xyl

High-resolution crystal structures of alpha-L-arabinofuranosidase from Geobacillus stearothermophilus T-6, a family 51 glycosidase, are described. The enzyme is a hexamer, and each monomer is organized into two domains: a (beta/alpha)8-barrel and a 12-stranded beta sandwich with jelly-roll topology. The structures of the Michaelis complexes with natural and synthetic substrates, and of the transient covalent arabinofuranosyl-enzyme intermediate represent two stable states in the double displacement mechanism, and allow thorough examination of the catalytic mechanism. The arabinofuranose sugar is tightly bound and distorted by an extensive network of hydrogen bonds. The two catalytic residues are 4.7 A apart, and together with other conserved residues contribute to the stabilization of the oxocarbenium ion-like transition state via charge delocalization and specific protein-substrate interactions. The enzyme is an anti-protonator, and a 1.7 A electrophilic migration of the anomeric carbon takes place during the hydrolysis.
PDB ID: 1QW8Download
MMDB ID: 24863
PDB Deposition Date: 2003/9/1
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 1.8  Å
Source Organism:
Similar Structures:
Biological Unit for 1QW8: hexameric; determined by author
Molecular Components in 1QW8
Label Count Molecule
Proteins (6 molecules)
Molecule annotation
Chemicals (6 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB