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Publication Abstract from PubMed

The human gut microbiota, which underpins nutrition and systemic health, is compositionally sensitive to the availability of complex carbohydrates in the diet. The Bacteroidetes comprise a dominant phylum in the human gut microbiota whose members thrive on dietary and endogenous glycans by employing a diversity of highly specific, multi-gene polysaccharide utilization loci (PUL), which encode a variety of carbohydrases, transporters, and sensor/regulators. PULs invariably also encode surface glycan-binding proteins (SGBPs) that play a central role in saccharide capture at the outer membrane. Here, we present combined biophysical, structural, and in vivo characterization of the two SGBPs encoded by the Bacteroides ovatus mixed-linkage beta-glucan utilization locus (MLGUL), thereby elucidating their key roles in the metabolism of this ubiquitous dietary cereal polysaccharide. In particular, molecular insight gained through several crystallographic complexes of SGBP-A and SGBP-B with oligosaccharides reveals that unique shape complementarity of binding platforms underpins specificity for the kinked MLG backbone vis-a-vis linear beta-glucans. Reverse-genetic analysis revealed that both the presence and binding ability of the SusD homolog BoSGBPMLG-A are essential for growth on MLG, whereas the divergent, multi-domain BoSGBPMLG-B is dispensable but may assist in oligosaccharide scavenging from the environment. The synthesis of these data illuminates the critical role SGBPs play in concert with other MLGUL components, reveals new structure-function relationships among SGBPs, and provides fundamental knowledge to inform future (meta)genomic, biochemical, and microbiological analyses of the human gut microbiota.

Surface glycan-binding proteins are essential for cereal beta-glucan utilization by the human gut symbiont Bacteroides ovatus.,Tamura K, Foley MH, Gardill BR, Dejean G, Schnizlein M, Bahr CME, Louise Creagh A, van Petegem F, Koropatkin NM, Brumer H Cell Mol Life Sci. 2019 May 6. pii: 10.1007/s00018-019-03115-3. doi:, 10.1007/s00018-019-03115-3. PMID:31062073^[1]

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