Structural basis of lipopolysaccharide assembly by the outer membrane translocon holo-complex
Lipopolysaccharide (LPS) assembly at the surfaces-exposed leaflet of the bacterial outer membrane (OM) is mediated by the OM LPS translocon. An essential transmembrane β-barrel protein, LptD, and a cognate lipoprotein, LptE, translocate LPS selectively into the OM external leaflet via a poorly understood mechanism. Here, we characterize two additional translocon subunits, the lipoproteins LptM and LptY (formerly YedD). We use single-particle cryo-EM analysis, functional assays and molecular dynamics simulations to visualize the roles of LptM and LptY at the translocon holo-complex LptDEMY, uncovering their impact on LptD conformational dynamics. Whereas LptY binds and stabilizes the periplasmic LptD β-taco domain that functions as LPS receptor, LptM intercalates the lateral gate of the β-barrel domain, promoting its opening and access by LPS. Remarkably, we demonstrate a conformational switch of the LptD β-taco/β-barrel interface alternating between contracted and extended states. β-strand 1 of LptD, which defines the mobile side of the lateral gate, binds LPS and performs a stroke movement toward the external leaflet during the contracted-to-extended state transition. Our findings support a detailed mechanistic framework explaining the selective transport of LPS to the membrane external leaflet.
Authors
- Rémi Fronzes (ORCID: https://orcid.org/0000-0003-3031-9824)
- Yves Quentin (ORCID: https://orcid.org/0000-0001-8248-0586)
- Axel Siroy (ORCID: https://orcid.org/0000-0002-8013-3596)
- Anne Caumont‐Sarcos
- Stéphanie Balor (ORCID: https://orcid.org/0000-0001-6828-0377)
- Phillip J. Stansfeld (ORCID: https://orcid.org/0000-0001-8800-7669)
- Dominik Gurvič (ORCID: https://orcid.org/0000-0002-0159-9209)
- Julien Marcoux (ORCID: https://orcid.org/0000-0001-7321-7436)
- Raffaele Ieva (ORCID: https://orcid.org/0000-0002-3405-0650)
- Carine Froment (ORCID: https://orcid.org/0000-0003-3688-5560)
- Yassin A. Abuta’a
- Haoxiang Chen (ORCID: https://orcid.org/0009-0009-6532-4907)
- Violette Morales (ORCID: https://orcid.org/0009-0008-8868-5273)
- Maurine Marteau
Institutions
- Centre National de la Recherche Scientifique (FR)
- Université Toulouse III - Paul Sabatier (FR)
- Université de Bordeaux (FR)
- Université Fédérale de Toulouse Midi-Pyrénées (FR)
- Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR)
- University of Warwick (GB)
- Institut de Recherche Interdisciplinaire de Grenoble (FR)
- Centre de Biologie du Développement (FR)
- Institut de Pharmacologie et de Biologie Structurale (FR)
- Institut Européen de Chimie et Biologie (FR)
- Laboratoire de Microbiologie et Génétique Moléculaires (FR)
- Institut Polytechnique de Bordeaux (FR)
- French Clinical Research Infrastructure Network (FR)
- Laboratoire de Microbiologie Fondamentale et Pathogénicité (FR)
Publication Details
- Journal
- Nature Communications
- Published
- 2025-11-24
- DOI
- https://doi.org/10.1038/s41467-025-65370-2
- Citations
- 1
- Primary Topic
- Bacterial Genetics and Biotechnology
- Type
- article
- Field-Weighted Citation Impact
- 1.82
Funders
- University of Warwick
- Agence Nationale de la Recherche
- China Scholarship Council
- Centre National de la Recherche Scientifique
- National Institutes of Health
- Medical Research Council
- Engineering and Physical Sciences Research Council
- Biotechnology and Biological Sciences Research Council