{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T05:54:56Z","timestamp":1787032496099,"version":"build-2736575974"},"posted":{"date-parts":[[2026,5,10]]},"group-title":"Microbiology","reference-count":87,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,5,10]],"date-time":"2026-05-10T00:00:00Z","timestamp":1778371200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/www.biorxiv.org\/about\/FAQ#license"}],"funder":[{"name":"NIH","award":["R35GM128777"],"award-info":[{"award-number":["R35GM128777"]}]},{"DOI":"10.13039\/100000875","name":"Pew Charitable Trusts","doi-asserted-by":"crossref","award":["PEW-00033055"],"award-info":[{"award-number":["PEW-00033055"]}],"id":[{"id":"10.13039\/100000875","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/100000001","name":"U.S. National Science Foundation","doi-asserted-by":"crossref","award":["2021318502"],"award-info":[{"award-number":["2021318502"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,5,10]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                <jats:p>\n                  Members of the Mammalian Cell Entry (MCE) superfamily interact with other proteins to form diverse architectures for the transport of hydrophobic molecules across the cell envelope in Gram-negative bacteria. Some of these trans-envelope MCE protein complexes include a PqiC-like outer membrane (OM) lipoprotein component. The best-studied member of this group of OM lipoproteins is\n                  <jats:italic>E. coli<\/jats:italic>\n                  PqiC, from the PqiABC system, which can form an octameric ring. How PqiC-like lipoproteins interact with their MCE protein binding partners to facilitate transport is not well understood. Here we report the cryo-electron microscopy structures of\n                  <jats:italic>Pseudomonas aeruginosa<\/jats:italic>\n                  PA3214, a homolog of PqiC, in the context of the full MCE transport PA3211-PA3214 system. Our structure provides insight into the biological assembly of the lipoprotein and interactions with its binding partner, MCE protein PA3213. We utilize deep mutational scanning to identify functionally important sites in\n                  <jats:italic>E. coli<\/jats:italic>\n                  PqiC in an unbiased manner. Through phenotypic and biochemical experiments, we characterize the interactions of the lipoproteins PqiC and PA3214 with their associated MCE proteins PqiB and PA3213, thus providing a model for how some MCE proteins employ a C-terminal peptide to mediate key interactions with their cognate lipoproteins at the OM.\n                <\/jats:p>","DOI":"10.64898\/2026.05.09.724024","type":"posted-content","created":{"date-parts":[[2026,5,10]],"date-time":"2026-05-10T14:35:15Z","timestamp":1778423715000},"source":"Crossref","is-referenced-by-count":1,"title":["Interactions of outer membrane lipoproteins\n                  <i>P. aeruginosa<\/i>\n                  PA3214 and\n                  <i>E. coli<\/i>\n                  PqiC with their MCE protein binding partners, PA3213 and PqiB"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8291-7722","authenticated-orcid":false,"given":"Sabrina I.","family":"Giacometti","sequence":"first","affiliation":[{"name":"Department of Biology, Johns Hopkins University, Baltimore, MD, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6050-2219","authenticated-orcid":false,"given":"Nicolas","family":"Coudray","sequence":"additional","affiliation":[{"name":"Department of Biology, Johns Hopkins University, Baltimore, MD, USA"},{"name":"Applied Bioinformatics Laboratories, New York University School of Medicine, New York, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0621-1303","authenticated-orcid":false,"given":"Rachel L.","family":"Redler","sequence":"additional","affiliation":[{"name":"Structural Biochemistry Group; Department of Biology, Chemistry, and Pharmacy; Freie Universit\u00e4t Berlin"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0624-6178","authenticated-orcid":false,"given":"Gira","family":"Bhabha","sequence":"additional","affiliation":[{"name":"Department of Biology, Johns Hopkins University, Baltimore, MD, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2570-0404","authenticated-orcid":false,"given":"Damian C.","family":"Ekiert","sequence":"additional","affiliation":[{"name":"Department of Biology, Johns Hopkins University, Baltimore, MD, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026051302000876000_2026.05.09.724024v1.1","doi-asserted-by":"publisher","DOI":"10.1038\/nrmicro1839"},{"key":"2026051302000876000_2026.05.09.724024v1.2","doi-asserted-by":"publisher","DOI":"10.1021\/acs.chemrev.0c00587"},{"key":"2026051302000876000_2026.05.09.724024v1.3","doi-asserted-by":"publisher","DOI":"10.1042\/BST20211030"},{"key":"2026051302000876000_2026.05.09.724024v1.4","doi-asserted-by":"publisher","DOI":"10.1016\/j.sbi.2020.03.005"},{"key":"2026051302000876000_2026.05.09.724024v1.5","doi-asserted-by":"crossref","first-page":"102429","DOI":"10.1016\/j.sbi.2022.102429","article-title":"Structure and mechanism of the bacterial lipid ABC transporter, MlaFEDB","volume":"76","year":"2022","journal-title":"Curr Opin Struct Biol"},{"key":"2026051302000876000_2026.05.09.724024v1.6","doi-asserted-by":"publisher","DOI":"10.1111\/nyas.14239"},{"key":"2026051302000876000_2026.05.09.724024v1.7","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1515\/hsz-2019-0326","article-title":"Transport mechanism of Mycobacterium tuberculosis MmpL\/S family proteins and implications in pharmaceutical targeting","volume":"401","year":"2020","journal-title":"Biol Chem"},{"key":"2026051302000876000_2026.05.09.724024v1.8","doi-asserted-by":"publisher","DOI":"10.1146\/annurev-cellbio-120420-022914"},{"key":"2026051302000876000_2026.05.09.724024v1.9","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.2015556117"},{"key":"2026051302000876000_2026.05.09.724024v1.10","doi-asserted-by":"publisher","DOI":"10.1016\/j.jmb.2024.168891"},{"key":"2026051302000876000_2026.05.09.724024v1.11","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.2321512121"},{"key":"2026051302000876000_2026.05.09.724024v1.12","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pgen.1010096"},{"key":"2026051302000876000_2026.05.09.724024v1.13","doi-asserted-by":"publisher","DOI":"10.1016\/j.cell.2017.03.019"},{"key":"2026051302000876000_2026.05.09.724024v1.14","doi-asserted-by":"publisher","DOI":"10.7554\/eLife.62518"},{"key":"2026051302000876000_2026.05.09.724024v1.15","doi-asserted-by":"publisher","DOI":"10.1016\/j.cell.2020.03.030"},{"key":"2026051302000876000_2026.05.09.724024v1.16","doi-asserted-by":"publisher","DOI":"10.1038\/s41586-023-06366-0"},{"key":"2026051302000876000_2026.05.09.724024v1.17","doi-asserted-by":"crossref","unstructured":"Santarossa, C. 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