1gny
From Proteopedia
XYLAN-BINDING MODULE CBM15
Structural highlights
Function[XY10C_CELJA] Endo-acting xylanase which specifically cleaves internal linkages on the xylan backbone, releasing xylooligosaccharides. Is able to hydrolyze oat spelt xylan, the arabinoxylans from wheat and rye, and glucuronoxylan. Also displays very low activity against xylooligosaccharides. During the xylan degradation process, Xyn10C may act on the soluble xylans and long xylooligosaccharides products released by the secreted xylanases Xyn11A, Xyn11B and Xyn10A.[1] [2] Publication Abstract from PubMedThe recycling of photosynthetically fixed carbon by the action of microbial glycoside hydrolases is a key biological process. The consortium of degradative enzymes involved in this process frequently display catalytic modules appended to one or more noncatalytic carbohydrate-binding modules (CBMs). CBMs play a central role in the optimization of the catalytic activity of plant cell wall hydrolases through their binding to specific plant structural polysaccharides. Despite their pivotal role in the biodegradation of plant biomass, the mechanism by which these proteins recognize their target ligands is unclear. This report describes the structure of a xylan-binding CBM (CBM15) in complex with its ligand. This module, derived from Pseudomonas cellulosa xylanase Xyn10C, binds to both soluble xylan and xylooligosaccharides. The three-dimensional crystal structure of CBM15 bound to xylopentaose has been solved by x-ray crystallography to a resolution of 1.6 A. The protein displays a similar beta-jelly roll fold to that observed in many other families of binding-modules. A groove, 20-25 A in length, on the concave surface of one of the beta-sheets presents two tryptophan residues, the faces of which are orientated at approximately 240 degrees to one another. These form-stacking interactions with the n and n+2 sugars of xylopentaose complementing the approximate 3-fold helical structure of this ligand in the binding cleft of CBM15. In four of the five observed binding subsites, the 2' and 3' hydroxyls of the bound ligand are solvent-exposed, providing an explanation for the capacity of this xylan-binding CBM to accommodate the highly decorated xylans found in the plant cell wall. Structure of a family 15 carbohydrate-binding module in complex with xylopentaose. Evidence that xylan binds in an approximate 3-fold helical conformation.,Szabo L, Jamal S, Xie H, Charnock SJ, Bolam DN, Gilbert HJ, Davies GJ J Biol Chem. 2001 Dec 28;276(52):49061-5. Epub 2001 Oct 11. PMID:11598143[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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