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Ascertaining the biochemical function of an essential pectin methylesterase in the gut microbe bacteroides thetaiotaomicron

Lookup NU author(s): Dr Arnaud Basle


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© 2020 Duan et al.Pectins are a major dietary nutrient source for the human gut microbiota. The prominent gut microbe Bacteroides thetaiotaomicron was recently shown to encode the founding member (BT1017) of a new family of pectin methylesterases essential for the metabolism of the complex pectin rhamnogalacturonan-II (RG-II). However, biochemical and structural knowledge of this family is lacking. Here, we showed that BT1017 is critical for the metabolism of an RG-II–derived oligosaccharide DBT1017oligoB generated by a BT1017 deletion mutant (DBT1017) during growth on carbohydrate extract from apple juice. Structural analyses of DBT1017oligoB using a combination of enzymatic, mass spectrometric, and NMR approaches revealed that it is a bimethylated nonaoligosaccharide (GlcA-b1,4-(2-O-Me-Xyl-a1,3)-Fuca1,4-(GalA-b1,3)-Rha-a1,3-Api-b1,2-(Araf-a1,3)-(GalA-a1,4)GalA) containing components of the RG-II backbone and its side chains. We showed that the catalytic module of BT1017 adopts an a/b-hydrolase fold, consisting of a central twisted 10-stranded b-sheet sandwiched by several a-helices. This constitutes a new fold for pectin methylesterases, which are predominantly right-handed b-helical proteins. Bioinformatic analyses revealed that the family is dominated by sequences from prominent genera of the human gut microbiota, including Bacteroides and Prevotella. Our re-sults not only highlight the critical role played by this family of enzymes in pectin metabolism but also provide new insights into the molecular basis of the adaptation of B. thetaiotaomicron to the human gut.

Publication metadata

Author(s): Duan C-J, Basle A, Liberato MV, Gray J, Nepogodiev SA, Field RA, Juge N, Ndeh D

Publication type: Article

Publication status: Published

Journal: Journal of Biological Chemistry

Year: 2020

Volume: 295

Issue: 52

Pages: 18625-18637

Print publication date: 25/12/2020

Online publication date: 23/10/2020

Acceptance date: 02/04/2016

ISSN (print): 0021-9258

ISSN (electronic): 1083-351X

Publisher: American Society for Biochemistry and Molecular Biology Inc.


DOI: 10.1074/jbc.RA120.014974

PubMed id: 33097594


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