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Bell, Andrew, Brunt, Jason, Crost, Emmanuelle, Vaux, Laura, Nepravishta, Ridvan, Owen, David, Latousakis, Dimitrios, Xiao, An, Li, Wanqing, Chen, Xi, Walsh, Martin A., Claesen, Jan, Angulo, Jesus 
ORCID: https://orcid.org/0000-0001-7250-5639, Thomas, Gavin H. and Juge, Nathalie
(2019)
Elucidation of a novel sialic acid metabolism pathway in mucus-foraging bacteria unravels mechanisms of adaptation to the gut.
Nature Microbiology, 4.
2393–2404.
ISSN 2058-5276
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Abstract
N-acetylneuraminic acid (Neu5Ac), the most abundant sialic acid form in humans, is commonly found in a terminal location on colonic mucins glycans where it is a much-coveted source of nutrients for gut bacteria. The mucin-foraging strategy of the human gut symbiont Ruminococcus gnavus is associated with the expression of an intramolecular trans-sialidase (IT-sialidase) that targets and cleaves off terminal α2–3 -linked Neu5Ac from glycoproteins, releasing 2,7-anhydro-Neu5Ac instead of Neu5Ac. Using a combination of in silico, molecular, biochemical and structural approaches, we have unravelled a unique metabolic pathway leading to the transport and metabolism of 2,7-anhydro-Neu5Ac which is underpinned by the exquisite specificity of the sialic acid transporter. The substrate binding protein, which forms part of a sialic acid transporter (SAT2) in R. gnavus ATCC29149, is specific to 2,7-anhydro-Neu5Ac, as shown by fluorescence spectroscopy, isothermal titration calorimetry (ITC), and saturation transfer difference nuclear magnetic resonance spectroscopy (STD NMR). Once inside the cell, 2,7-anhydro-Neu5Ac is converted into Neu5Ac via a novel enzymatic reaction catalysed by an oxidoreductase, RgNanOx. Following this conversion, Neu5Ac is then catabolised into N-acetylmannosamine (ManNAc) and pyruvate via the action of a Neu5Ac specific aldolase that is structurally and biochemically typical of NanA-like enzymes, as shownby X-ray crystallography of RgNanA wild-type and site-directed active site mutant K167A in complex with Neu5Ac. We confirmed the importance of this metabolic pathway in vivo by generating a R. gnavus nan cluster deletion mutant that lost the ability to grow on sialylated substrates. We showed that in gnotobiotic mice colonised with R. gnavus wild-type and mutant strains, the fitness of the nan mutant was significantly impaired as compared to the wild-type strain with a reduced ability to colonise the mucus layer. Overall, our study revealed a novel sialic acid pathway in bacteria, which has significant implications for the spatial adaptation of mucin-foraging gut symbionts in health and disease.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | sdg 3 - good health and well-being ,/dk/atira/pure/sustainabledevelopmentgoals/good_health_and_well_being |
| Faculty \ School: | Faculty of Science > School of Pharmacy |
| UEA Research Groups: | Faculty of Science > Research Groups > Pharmaceutical Materials and Soft Matter |
| Depositing User: | LivePure Connector |
| Date Deposited: | 13 Sep 2019 09:30 |
| Last Modified: | 14 Dec 2023 03:21 |
| URI: | https://ueaeprints.uea.ac.uk/id/eprint/72191 |
| DOI: | 10.1038/s41564-019-0590-7 |
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