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Raffinose and panose binding protein from Bifidobacterium animalis subsp. lactis Bl-04, bound with panose
Structural highlights
FunctionPublication Abstract from PubMedThe molecular details and impact of oligosaccharide uptake by distinct human gut microbiota (HGM) are currently not well understood. Non-digestible dietary galacto- and gluco-alpha-(1,6)-oligosaccharides from legumes and starch, respectively, are preferentially fermented by mainly bifidobacteria and lactobacilli in the human gut. Here we show that the solute binding protein (BlG16BP) associated with an ATP binding cassette (ABC) transporter from the probiotic Bifidobacterium animalis subsp. lactis Bl-04 binds alpha-(1,6)-linked glucosides and galactosides of varying size, linkage, and monosaccharide composition with preference for the trisaccharides raffinose and panose. This preference is also reflected in the alpha-(1,6)-galactoside uptake profile of the bacterium. Structures of BlG16BP in complex with raffinose and panose revealed the basis for the remarkable ligand binding plasticity of BlG16BP, which recognizes the non-reducing alpha-(1,6)-diglycoside in its ligands. BlG16BP homologues occur predominantly in bifidobacteria and a few Firmicutes but lack in other HGMs. Among seven bifidobacterial taxa, only those possessing this transporter displayed growth on alpha-(1,6)-glycosides. Competition assays revealed that the dominant HGM commensal Bacteroides ovatus was out-competed by B. animalis subsp. lactis Bl-04 in mixed cultures growing on raffinose, the preferred ligand for the BlG16BP. By comparison, B. ovatus mono-cultures grew very efficiently on this trisaccharide. These findings suggest that the ABC-mediated uptake of raffinose provides an important competitive advantage, particularly against dominant Bacteroides that lack glycan-specific ABC-transporters. This novel insight highlights the role of glycan transport in defining the metabolic specialization of gut bacteria. An ATP Binding Cassette Transporter Mediates the Uptake of alpha-(1,6)-Linked Dietary Oligosaccharides in Bifidobacterium and Correlates with Competitive Growth on These Substrates.,Ejby M, Fredslund F, Andersen JM, Vujicic Zagar A, Henriksen JR, Andersen TL, Svensson B, Slotboom DJ, Abou Hachem M J Biol Chem. 2016 Sep 16;291(38):20220-31. doi: 10.1074/jbc.M116.746529. Epub, 2016 Aug 8. PMID:27502277[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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