Differences in protein structural regions that impact functional specificity in GT2 family β- Glucan synthases
journal contributionposted on 11.02.2021, 23:49 by Daniel P Oehme, Thomas Shafee, Matthew T Downton, Tony Bacic, Monika Doblin
© 2019 Oehme, Shafee et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Most cell wall and secreted β-glucans are synthesised by the CAZy Glycosyltransferase 2 family (www.cazy.org), with different members catalysing the formation of (1,4)-β-, (1,3)-β-, or both (1,4)- and (1,3)-β-glucosidic linkages. Given the distinct physicochemical properties of each of the resultant β-glucans (cellulose, curdlan, and mixed linkage glucan, respectively) are crucial to their biological and biotechnological functions, there is a desire to understand the molecular evolution of synthesis and how linkage specificity is determined. With structural studies hamstrung by the instability of these proteins to solubilisation, we have utilised in silico techniques and the crystal structure for a bacterial cellulose synthase to further understand how these enzymes have evolved distinct functions. Sequence and phylogenetic analyses were performed to determine amino acid conservation, both family-wide and within each sub-family. Further structural analysis centred on comparison of a bacterial curdlan synthase homology model with the bacterial cellulose synthase crystal structure, with molecular dynamics simulations performed with their respective β-glucan products bound in the trans-membrane channel. Key residues that differentially interact with the different β-glucan chains and have sub-family-specific conservation were found to reside at the entrance of the trans-membrane channel. The linkage-specific catalytic activity of these enzymes and hence the type of β-glucan chain built is thus likely determined by the different interactions between the proteins and the first few glucose residues in the channel, which in turn dictates the position of the acceptor glucose. The sequence-function relationships for the bacterial β- glucan synthases pave the way for extending this understanding to other kingdoms, such as plants.
This work was funded by a grant from the Australia Research Council to the ARC Centre of Excellence in Plant Cell Walls (to DPO, MSD and AB) (CE110001007); and the Victorian Life Sciences Computation Initiative (VLSCI) grant numbers "VR0319'' on its Peak Computing Facility at the University of Melbourne, an initiative of the Victorian State Government (to DPO). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Australia Research Council | CE110001007
Victorian Life Sciences Computation Initiative (VLSCI) | VR0319
Article NumberARTN e0224442
PublisherPublic Library of Science
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Science & TechnologyMultidisciplinary SciencesScience & Technology - Other TopicsPLANT CELLULOSE SYNTHASEMOLECULAR-DYNAMICSSTRUCTURE PREDICTIONCURDLAN SYNTHASECATALYTIC DOMAINFORCE-FIELDPILZ DOMAININ-VITROBIOSYNTHESISMEMBRANEGlucosyltransferasesbeta-GlucansBacterial ProteinsPhylogenyAmino Acid SequenceCatalytic DomainConserved SequenceProtein ConformationStructure-Activity RelationshipHydrogen BondingModels, MolecularGeneral Science & Technology