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Structure of the GH76 alpha-mannanase homolog, BT2949, from the gut symbiont Bacteroides thetaiotaomicron

Lookup NU author(s): Dr Fiona Cuskin, Emeritus Professor Harry Gilbert



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


The large bowel microbiota, a complex ecosystem resident within the gastrointestinal tract of all human beings and large mammals, functions as an essential, nonsomatic metabolic organ, hydrolysing complex dietary polysaccharides and modulating the host immune system to adequately tolerate ingested antigens. A significant member of this community, Bacteroides thetaiotaomicron, has evolved a complex system for sensing and processing a wide variety of natural glycoproducts in such a way as to provide maximum benefit to itself, the wider microbial community and the host. The immense ability of B. thetaiotaomicron as a ` glycan specialist' resides in its enormous array of carbohydrate-active enzymes, many of which are arranged into polysaccharide-utilization loci (PULs) that are able to degrade sugar polymers that are often inaccessible to other gut residents, notably alpha-mannan. The B. thetaiotaomicron genome encodes ten putative alpha-mannanases spread across various PULs; however, little is known about the activity of these enzymes or the wider implications of alpha-mannan metabolism for the health of both the microbiota and the host. In this study, SAD phasing of a selenomethionine derivative has been used to investigate the structure of one such B. thetaiotaomicron enzyme, BT2949, which belongs to the GH76 family of alpha-mannanases. BT2949 presents a classical (alpha/alpha)(6)-barrel structure comprising a large extended surface cleft common to other GH76 family members. Analysis of the structure in conjunction with sequence alignments reveals the likely location of the catalytic active site of this noncanonical GH76.

Publication metadata

Author(s): Thompson AJ, Cuskin F, Spears RJ, Dabin J, Turkenburg JP, Gilbert HJ, Davies GJ

Publication type: Article

Publication status: Published

Journal: Acta Crystallographica Section D Biological Crystallography

Year: 2015

Volume: 71

Issue: 2

Pages: 408-415

Print publication date: 01/02/2015

Acceptance date: 01/12/2014

Date deposited: 26/08/2015

ISSN (print): 0907-4449

ISSN (electronic): 1399-0047

Publisher: Wiley-Blackwell Publishing, Inc,


DOI: 10.1107/S1399004714026443


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