1w9f

CBM29-2 mutant R112A: Probing the Mechanism of Ligand Recognition by Family 29 Carbohydrate Binding Modules

spinqualitylabelsall models 1w9f, resolution 2.25Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1w9f is a 2 chain structure with sequence from Piromyces sp. 'equi'. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.25Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q9C171_PIREQ Publication Abstract from PubMed The recycling of photosynthetically fixed carbon, by the action of microbial plant cell wall hydrolases, is integral to one of the major geochemical cycles and is of considerable industrial importance. Non-catalytic carbohydrate-binding modules (CBMs) play a key role in this degradative process by targeting hydrolytic enzymes to their cognate substrate within the complex milieu of polysaccharides that comprise the plant cell wall. Family 29 CBMs have, thus far, only been found in an extracellular multienzyme plant cell wall-degrading complex from the anaerobic fungus Piromyces equi, where they exist as a CBM29-1:CBM29-2 tandem. Here we present both the structure of the CBM29-1 partner, at 1.5 A resolution, and examine the importance of hydrophobic stacking interactions as well as direct and solvent-mediated hydrogen bonds in the binding of CBM29-2 to different polysaccharides. CBM29 domains display unusual binding properties, exhibiting specificity for both beta-manno- and beta-gluco-configured ligands such as mannan, cellulose, and glucomannan. Mutagenesis reveals that "stacking" of tryptophan residues in the n and n+2 subsites plays a critical role in ligand binding, whereas the loss of tyrosine-mediated stacking in the n+4 subsite reduces, but does not abrogate, polysaccharide recognition. Direct hydrogen bonds to ligand, such as those provided by Arg-112 and Glu-78, play a pivotal role in the interaction with both mannan and cellulose, whereas removal of water-mediated interactions has comparatively little effect on carbohydrate binding. The interactions of CBM29-2 with the O2 of glucose or mannose contribute little to binding affinity, explaining why this CBM displays dual gluco/manno specificity. Probing the mechanism of ligand recognition in family 29 carbohydrate-binding modules.,Flint J, Bolam DN, Nurizzo D, Taylor EJ, Williamson MP, Walters C, Davies GJ, Gilbert HJ J Biol Chem. 2005 Jun 24;280(25):23718-26. Epub 2005 Mar 22. PMID:15784618 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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