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Publication Abstract from PubMed

Complex glycans that evade our digestive system are major nutrients that feed the human gut microbiota (HGM). The prevalence of Bacteroidetes in the HGM of populations worldwide is engendered by the evolution of Polysaccharide Utilization Locus (PUL), which encode concerted protein systems to utilize the myriad complex glycans in our diets. Despite their crucial roles in glycan recognition and transport, cell-surface glycan-binding proteins (SGBPs) remained understudied cogs in the PUL machinery. Here, we report the structural and biochemical characterization of a suite of SGBP-A and SGBP-B structures from three syntenic beta(1,3)-glucan utilization loci (1,3GULs) from Bacteroides thetaiotaomicron (Bt), B. uniformis (Bu), and B. fluxus (Bf), which have varying specificities for distinct beta-glucans. Ligand complexes provide definitive insight into beta(1,3)-glucan selectivity in the HGM, including structural features enabling dual beta(1,3)-glucan/mixed-linkage beta(1,3)/beta(1,4)-glucan binding capability in some orthologs. The tertiary structural conservation of SusD-like SGBPs-A is juxtaposed with the diverse architectures and binding modes of the SGBPs-B. Specifically, the structures of the tri-modular BtSGBP-B and BuSGBP-B revealed a tandem repeat of Carbohydrate-Binding Module-Like domains connected by long linkers. In contrast, BfSGBP-B comprises a bi-modular architecture with a distinct beta-barrel domain at the C-terminus that bears a shallow binding canyon. The molecular insights obtained here contribute to our fundamental understanding of HGM function, which in turn may inform tailored microbial intervention therapies.

Distinct protein architectures mediate species-specific beta-glucan binding and metabolism in the human gut microbiota.,Tamura K, Dejean G, Van Petegem F, Brumer H J Biol Chem. 2021 Feb 12:100415. doi: 10.1016/j.jbc.2021.100415. PMID:33587952^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.