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|Title:||Structural analysis and insights into the glycon specificity of the rice GH1 Os7BGlu26 β-D-mannosidase||Authors:||Robinson, Robert Charles
Ketudat Cairns, James R.
|Issue Date:||2013||Source:||Tankrathok, A., Iglesias-Fernández, J., Luang, S., Robinson, R. C., Kimura, A., Rovira, C., et al. (2013). Structural analysis and insights into the glycon specificity of the rice GH1 Os7BGlu26 β-D-mannosidase. Acta Crystallographica Section D Biological Crystallography, 69(10), 2124-2135.||Series/Report no.:||Acta Crystallographica Section D Biological Crystallography||Abstract:||Rice Os7BGlu26 is a GH1 family glycoside hydrolase with a threefold higher kcat/Km value for 4-nitrophenyl β-D-mannoside (4NPMan) compared with 4-nitrophenyl β-D-glucoside (4NPGlc). To investigate its selectivity for β-D-mannoside and β-D-glucoside substrates, the structures of apo Os7BGlu26 at a resolution of 2.20 Å and of Os7BGlu26 with mannose at a resolution of 2.45 Å were elucidated from isomorphous crystals in space group P212121. The (β/α)8-barrel structure is similar to other GH1 family structures, but with a narrower active-site cleft. The Os7BGlu26 structure with D-mannose corresponds to a product complex, with β-D-mannose in the 1S5 skew-boat conformation. Docking of the 1S3, 1S5, 2SO and 3S1 pyranose-ring conformations of 4NPMan and 4NPGlc substrates into the active site of Os7BGlu26 indicated that the lowest energies were in the 1S5 and 1S3 skew-boat conformations. Comparison of these docked conformers with other rice GH1 structures revealed differences in the residues interacting with the catalytic acid/base between enzymes with and without β-D-mannosidase activity. The mutation of Tyr134 to Trp in Os7BGlu26 resulted in similar kcat/Km values for 4NPMan and 4NPGlc, while mutation of Tyr134 to Phe resulted in a 37-fold higher kcat/Km for 4NPMan than 4NPGlc. Mutation of Cys182 to Thr decreased both the activity and the selectivity for β-D-mannoside. It was concluded that interactions with the catalytic acid/base play a significant role in glycon selection.||URI:||https://hdl.handle.net/10356/82124
|ISSN:||0907-4449||DOI:||10.1107/S0907444913020568||Rights:||© 2013 International Union of Crystallography.||Fulltext Permission:||none||Fulltext Availability:||No Fulltext|
|Appears in Collections:||SBS Journal Articles|
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