5ofj

Crystal structure of N-terminal domain of bifunctional CbXyn10C

spinqualitylabelsall models 5ofj, resolution 1.34Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 5ofj is a 1 chain structure with sequence from Caldicellulosiruptor bescii DSM 6725. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.34Å Ligands: EDO, FLC Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function B9MKT7_CALBD Publication Abstract from PubMed Bifunctional glycoside hydrolases have potential for cost saving in enzymatic decomposition of plant cell wall polysaccharides for biofuels and bio-based chemicals. The N-terminal GH10 domain of a bifunctional multimodular enzyme CbXyn10C/Cel48B from Caldicellulosiruptor bescii, is an enzyme able to degrade xylan and cellulose simultaneously. However, the molecular mechanism underlying its substrate promiscuity has not been elucidated. Herein, we discovered that the binding cleft of CbXyn10C would have at least six sugar binding subsites by using isothermal titration calorimetry analysis of the inactive E140Q/E248Q mutant with xylo- and cellooligosaccharides. This was confirmed by determining the catalytic efficiency of the wild-type enzyme on these oligosaccharides. The free form and complex structures of CbXyn10C with xylose- or glucose-configured oligosaccharide ligands were further obtained by crystallographic analysis and molecular modeling and docking. CbXyn10C was found to have a typical (beta/alpha)8-TIM barrel fold and "salad-bowl" shape of GH10 enzymes. In complex structure with xylo-oligosaccharides, seven sugar-binding subsites were found and many residues responsible for substrate interactions were identified. Site-directed mutagenesis indicated that six and ten amino acid residues were key residues for xylan and cellulose hydrolysis, respectively. The most important residues are centered on the subsites -2 and -1 near the cleavage site, while residues playing moderate roles could be located at more distal regions of the binding cleft. Manipulating the residues directly or indirectly interacting with substrates in the distal regions improved the activity of CbXyn10C on xylan and cellulose. Most of the key residues for cellulase activity are conserved across GH10 xylanases. Revisiting randomly selected GH10 enzymes revealed unreported cellulase activity, indicating that the dual function may be a more common phenomenon than has been expected. Insights into the roles of non-catalytic residues in the active site of a GH10 xylanase with activity on cellulose.,Chu Y, Tu T, Penttinen L, Xue X, Wang X, Yi Z, Gong L, Rouvinen J, Luo H, Hakulinen N, Yao B, Su X J Biol Chem. 2017 Oct 3. pii: jbc.M117.807768. doi: 10.1074/jbc.M117.807768. PMID:28974575 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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