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BtuB TonB-dependent transporters and BtuG surface lipoproteins form stable complexes for vitamin B12 uptake in gut Bacteroides

Lookup NU author(s): Dr Javier Abellon-RuizORCiD, Dr Augustinas SilaleORCiD, Dr Andrew FreyORCiD, Dr Arnaud Basle, Professor Matthias TrostORCiD



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


© 2023, Springer Nature Limited.Vitamin B12 (cobalamin) is required for most human gut microbes, many of which are dependent on scavenging to obtain this vitamin. Since bacterial densities in the gut are extremely high, competition for this keystone micronutrient is severe. Contrasting with Enterobacteria, members of the dominant genus Bacteroides often encode several BtuB vitamin B12 outer membrane transporters together with a conserved array of surface-exposed B12-binding lipoproteins. Here we show that the BtuB transporters from Bacteroides thetaiotaomicron form stable, pedal bin-like complexes with surface-exposed BtuG lipoprotein lids, which bind B12 with high affinities. Closing of the BtuG lid following B12 capture causes destabilisation of the bound B12 by a conserved BtuB extracellular loop, causing translocation of the vitamin to BtuB and subsequent transport. We propose that TonB-dependent, lipoprotein-assisted small molecule uptake is a general feature of Bacteroides spp. that is important for the success of this genus in colonising the human gut.

Publication metadata

Author(s): Abellon-Ruiz J, Jana K, Silale A, Frey AM, Baslé A, Trost M, Kleinekathöfer U, van den Berg B

Publication type: Article

Publication status: Published

Journal: Nature Communications

Year: 2023

Volume: 14

Online publication date: 05/08/2023

Acceptance date: 27/07/2023

Date deposited: 01/09/2023

ISSN (electronic): 2041-1723

Publisher: Nature Publishing Group


DOI: 10.1038/s41467-023-40427-2

Data Access Statement: The data supporting the findings of this study are available from the corresponding authors upon reasonable request. The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the data set identifier: PXD038230. For X-ray structures coordinates and structure factors have been deposited in the Protein Data Bank with accession codes 8BMX for BtuG2-CNCbl, 8BMY for BtuG2-AdoCbl, 8BZM for BtuG2-Cbi, 8BM0 for BtuB2G2 and 8OKV for BtuG3-CNCbl. EM structure coordinates have been deposited in the Protein Data Bank and EM maps in the Electron Microscopy Data Bank with accession codes 8BLW and EMD-16114 for BtuB1G1, 8P98 and EMD-17575 for BtuB3G3-CNCbl state1 and 8P97 and EMD-17574 for BtuB3G3-CNCbl state2. The pdb model used for molecular replacement was previously deposited as 3DSM. Initial and final conformations for the molecular dynamics analysis have been deposited in Zenodo (

PubMed id: 37543597


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Funder referenceFunder name
214222/Z/18/ZWellcome Trust
215542/Z/19/ZWellcome Trust
Wellcome Trust