1wu6
From Proteopedia
Crystal structure of reducing-end-xylose releasing exo-oligoxylanase E70A mutant complexed with xylobiose
Structural highlights
FunctionREOX_HALH5 Hydrolyzes xylooligosaccharides with a degree of polymerization of greater than or equal to 3, releasing xylose from the reducing end. Only hydrolyzes the beta anomers of xylooligosaccharides, with inversion of anomeric configuration. Hydrolyzes the glucose and xylose-based trisaccharides where xylose is located at the -1 subsite, GXX, XXG and GXG. Does not hydrolyze xylan, chitosan, lichenan, curdlan or carboxymethylcellulose.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedReducing end xylose-releasing exo-oligoxylanase from Bacillus halodurans C-125 (Rex) hydrolyzes xylooligosaccharides whose degree of polymerization is greater than or equal to 3, releasing the xylose unit at the reducing end. It is a unique exo-type glycoside hydrolase that recognizes the xylose unit at the reducing end in a very strict manner, even discriminating the beta-anomeric hydroxyl configuration from the alpha-anomer or 1-deoxyxylose. We have determined the crystal structures of Rex in unliganded and complex forms at 1.35-2.20-A resolution and revealed the structural aspects of its three subsites ranging from -2 to +1. The structure of Rex was compared with those of endo-type enzymes in glycoside hydrolase subfamily 8a (GH-8a). The catalytic machinery of Rex is basically conserved with other GH-8a enzymes. However, subsite +2 is blocked by a barrier formed by a kink in the loop before helix alpha10. His-319 in this loop forms a direct hydrogen bond with the beta-hydroxyl of xylose at subsite +1, contributing to the specific recognition of anomers at the reducing end. Structural basis for the specificity of the reducing end xylose-releasing exo-oligoxylanase from Bacillus halodurans C-125.,Fushinobu S, Hidaka M, Honda Y, Wakagi T, Shoun H, Kitaoka M J Biol Chem. 2005 Apr 29;280(17):17180-6. Epub 2005 Feb 17. PMID:15718242[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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