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Lookup NU author(s): Dr Augustinas SilaleORCiD, Dr Andy Frey, Dr Adam HartORCiD, Dr Arnaud Basle, Professor Matthias TrostORCiD, Emeritus Professor Robert HirtORCiD, Professor Bert van den BergORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© The Author(s) 2025.The Gram-negative β-barrel assembly machinery (BAM) complex catalyses the folding and membrane insertion of newly synthesized β-barrel outer membrane proteins. The BAM is structurally conserved, but most studies have focused on Gammaproteobacteria. Here, using single-particle cryogenic electron microscopy, quantitative proteomics and functional assays, we show that the BAM complex is distinct within the Bacteroidota. Cryogenic electron microscopy structures of BAM complexes from the human gut symbiont Bacteroides thetaiotaomicron (3.3 Å) and the human oral pathogen Porphyromonas gingivalis (3.2 Å) show similar, seven-component complexes of ~325 kDa. The complexes are mostly extracellular and comprise canonical BamA and BamD; an integral, essential outer membrane protein, BamG, that associates with BamA; and four surface-exposed lipoproteins: BamH–K. Absent from the BAM in Pseudomonadota, BamG–K form a large, extracellular dome that may confer additional functionality to enable the folding and assembly of β-barrel–surface-exposed lipoprotein complexes that are a hallmark of the Bacteroidota. Our findings develop our understanding of fundamental biological processes in an important bacterial phylum.
Author(s): Silale A, Madej M, Mikruta K, Frey AM, Hart AJ, Basle A, Scavenius C, Enghild JJ, Trost M, Hirt RP, van den Berg B
Publication type: Article
Publication status: Published
Journal: Nature Microbiology
Year: 2025
Pages: epub ahead of print
Online publication date: 01/10/2025
Acceptance date: 21/08/2025
Date deposited: 13/10/2025
ISSN (electronic): 2058-5276
Publisher: Nature Research
URL: https://doi.org/10.1038/s41564-025-02132-2
DOI: 10.1038/s41564-025-02132-2
Data Access Statement: Pulldown proteomic mass spectrometry datasets and result files are referenced in ProteomeXchange (PXD058163) and available to download from MassIVE (MSV000096498; https://doi.org/10.25345/ C57W67J00). B. thetaiotaomicron membrane and P. gingivalis whole-cell mass spectrometry proteomics data have been depos ited to the ProteomeXchange Consortium via the PRIDE90 partner repository with the dataset identifiers PXD058903 for B. thetaiotaomi cron and PXD058905 for P. ginigivalis. Cryo-EM reconstructions and atomic coordinate files with the indicated accession numbers have been uploaded to the Electron Microscopy Data Bank (EMDB) and the Protein Data Bank (PDB): BtBAM class 1(EMD-52200 and 9HIS), BtBAM class 2 (EMD-52202 and 9HIV), BtBAM composite map and model (EMD 52209 and 9HJ3), PgBAM class 1 (EMD-52218 and 9HJM) and PgBAM class 2 (EMD-52219). All data that support the findings of this study are available within the Article and Supplementary Information.
PubMed id: 41034344
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