2xyl

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spinqualitylabelsall models 2xyl, resolution 1.9Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CELLULOMONAS FIMI XYLANASE/CELLULASE COMPLEXED WITH 2-DEOXY-2-FLUORO-XYLOBIOSE

Overview

The retaining beta-1,4-glycanase Cex from Cellulomonas fimi, a family 10, glycosyl hydrolase, hydrolyzes xylan 40-fold more efficiently than, cellulose. To gain insight into the nature of its preference for xylan, we, determined the crystal structure of the Cex catalytic domain (Cex-cd), trapped as its covalent 2-deoxy-2-fluoroxylobiosyl-enzyme intermediate to, 1.9 A resolution. Together with the crystal structure of unliganded Cex-cd, [White, A., et al. (1994) Biochemistry 33, 12546-12552] and the previously, determined crystal structure of the covalent, 2-deoxy-2-fluorocellobiosyl-Cex-cd intermediate [White, A., et al. (1996), Nat. Struct. Biol. 3, 149-154], this structure provides a convincing, rationale for the observed substrate specificity in Cex. Two active site, residues, Gln87 and Trp281, are found to sterically hinder the binding of, glucosides and must rearrange to accommodate these substrates. Such, rearrangements are not necessary for the binding of xylobiosides. The, importance of this observation was tested by examining the catalytic, behavior of the enzyme with Gln87 mutated to Met. This mutation had no, measurable effect on substrate affinity or turnover number relative to the, wild type enzyme, indicating that the Met side chain could accommodate the, glucoside moiety as effectively as the wild type Gln residue. Subsequent, mutagenesis studies will address the role of entropic versus enthalpic, contributions to binding by introducing side chains that might be more, rigid in the unliganded enzyme.

About this Structure

2XYL is a Single protein structure of sequence from Cellulomonas fimi. Active as Cellulose 1,4-beta-cellobiosidase, with EC number 3.2.1.91 Full crystallographic information is available from OCA.

Reference

Exploring the cellulose/xylan specificity of the beta-1,4-glycanase cex from Cellulomonas fimi through crystallography and mutation., Notenboom V, Birsan C, Warren RA, Withers SG, Rose DR, Biochemistry. 1998 Apr 7;37(14):4751-8. PMID:9537990

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