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Publication Abstract from PubMed

Bifidobacteria represent one of the first colonizers of human gut microbiota, providing to this ecosystem better health and nutrition. To maintain a mutualistic relationship, they have enzymes to degrade and use complex carbohydrates non-digestible by their hosts. To succeed in the densely populated gut environment, they evolved molecular strategies that remain poorly understood. Herein, we report a novel mechanism found in probiotic Bifidobacteria for the depolymerization of the ubiquitous 2-acetamido-2-deoxy-4-O-(beta-d-mannopyranosyl)-d-glucopyranose (Man-beta-1,4-GlcNAc), a disaccharide that composes the universal core of eukaryotic N-glycans. In contrast to Bacteroidetes, these Bifidobacteria have a specialist and strain-specific beta-mannosidase that contains three distinctive structural elements conferring high selectivity for Man-beta-1,4-GlcNAc: a lid that undergoes conformational changes upon substrate binding, a tryptophan residue swapped between the two dimeric subunits to accommodate the GlcNAc moiety, and a Rossmann fold subdomain strategically located near to the active site pocket. These key structural elements for Man-beta-1,4-GlcNAc specificity are highly conserved in Bifidobacterium species adapted to the gut of a wide range of social animals, including bee, pig, rabbit, and human. Together, our findings uncover an unprecedented molecular strategy employed by Bifidobacteria to selectively uptake carbohydrates from N-glycans in social hosts.

N-glycan Utilization by Bifidobacterium Gut Symbionts Involves a Specialist beta-Mannosidase.,Cordeiro RL, Pirolla RAS, Persinoti GF, Gozzo FC, de Giuseppe PO, Murakami MT J Mol Biol. 2019 Jan 11. pii: S0022-2836(19)30006-3. doi:, 10.1016/j.jmb.2018.12.017. PMID:30641082^[1]

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