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Solution structure of Family 1 Carbohydrate-Binding Module from Trichoderma reesei Cel7A with O-mannose residues at Thr1 and Ser3
Structural highlights
FunctionGUX1_HYPJE The biological conversion of cellulose to glucose generally requires three types of hydrolytic enzymes: (1) Endoglucanases which cut internal beta-1,4-glucosidic bonds; (2) Exocellobiohydrolases that cut the dissaccharide cellobiose from the non-reducing end of the cellulose polymer chain; (3) Beta-1,4-glucosidases which hydrolyze the cellobiose and other short cello-oligosaccharides to glucose. Publication Abstract from PubMedFamily 1 carbohydrate-binding modules (CBMs) are ubiquitous components of multi-modular fungal enzymes that degrade plant cell wall polysaccharides and bind specifically to cellulose. Native glycosylation of Family 1 CBMs has been shown to substantially impact multiple physical properties including thermal and proteolytic stability and cellulose binding affinity To gain molecular insights into the changes in CBM properties upon glycosylation, solution structures of two glycoforms of a Trichoderma reesei Family 1 CBM were studied by NMR spectroscopy: a glycosylated Family 1 CBM with a mannose group attached to both Thr1 and Ser3 and a second Family 1 CBM with single mannose groups attached to Thr1, Ser3, and Ser14. The structures clearly reveal that monosaccharides at both Ser3 and Ser14 on Family 1 CBMs present additional cellulose binding platforms, similar to well-characterized aromatic residues at the binding interface, which align to the cellulose surface. These results are in agreement with previous experimental work that demonstrated glycans at Ser3 and Ser14 impart significant improvements in binding affinity. Additionally, detailed analysis of the NMR structures and molecular simulations indicates that the protein backbone of the CBM is not significantly altered by attachment of monosaccharides, and that the mannose attached to Ser14 may be more flexible than the mannose at Ser3. Overall, this study reveals how Family 1 CBM structures are affected by covalent attachment of monosaccharides, which are likely important post-translational modifications of these common sub-domains of fungal plant cell wall degrading enzymes. This article is protected by copyright. All rights reserved. O-Glycosylation Effects on Family 1 Carbohydrate-Binding Module Solution Structures.,Happs RM, Guan X, Resch MG, Davis MF, Beckham GT, Tan Z, Crowley MF FEBS J. 2015 Aug 26. doi: 10.1111/febs.13500. PMID:26307003[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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