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| Title | LetA defines a structurally distinct transporter family involved in lipid trafficking. |
|---|---|
| Journal, issue, pages | bioRxiv, Year 2025 |
| Publish date | Mar 22, 2025 |
Authors | Cristina C Santarossa / Yupeng Li / Sara Yousef / Hale S Hasdemir / Carlos C Rodriguez / Max B Haase / Minkyung Baek / Nicolas Coudray / John G Pavek / Kimber N Focke / Annika L Silverberg / Carmelita Bautista / Johannes Yeh / Michael T Marty / David Baker / Emad Tajkhorshid / Damian C Ekiert / Gira Bhabha |
| PubMed Abstract | Membrane transport proteins translocate diverse cargos, ranging from small sugars to entire proteins, across cellular membranes. A few structurally distinct protein families have been described that ...Membrane transport proteins translocate diverse cargos, ranging from small sugars to entire proteins, across cellular membranes. A few structurally distinct protein families have been described that account for most of the known membrane transport processes. However, many membrane proteins with predicted transporter functions remain uncharacterized. We determined the structure of LetAB, a phospholipid transporter involved in outer membrane integrity, and found that LetA adopts a distinct architecture that is structurally and evolutionarily unrelated to known transporter families. LetA functions as a pump at one end of a ~225 Å long tunnel formed by its binding partner, MCE protein LetB, creating a pathway for lipid transport between the inner and outer membranes. Unexpectedly, the LetA transmembrane domains adopt a fold that is evolutionarily related to the eukaryotic tetraspanin family of membrane proteins, including TARPs and claudins. LetA has no detectable homology to known transport proteins, and defines a new class of membrane transporters. Through a combination of deep mutational scanning, molecular dynamics simulations, AlphaFold-predicted alternative states, and functional studies, we present a model for how the LetA-like family of membrane transporters may use energy from the proton-motive force to drive the transport of lipids across the bacterial cell envelope. |
External links | bioRxiv / PubMed:40166208 / PubMed Central |
| Methods | EM (single particle) |
| Resolution | 2.8 - 3.5 Å |
| Structure data | ![]() EMDB-49145: Local refinement of crosslinked LetA and LetB MCE Rings 1 and 2 (Map 1a) ![]() EMDB-49146: Local refinement of crosslinked LetB MCE Rings 2, 3 and 4 (Map 1b) ![]() EMDB-49147: Local refinement of crosslinked LetB MCE Rings 5, 6 and 7 (Map 1c) EMDB-49148: Intermembrane lipid transport complex LetAB from Escherichia coli (Crosslinked, Composite Map 1) ![]() EMDB-49149: Local refinement of LetA and LetB MCE Rings 1 and 2 (Map 2a) ![]() EMDB-49150: Local refinement of LetB MCE Rings 2, 3 and 4 (Map 2b) ![]() EMDB-49151: Local refinement of LetB MCE Rings 5, 6 and 7 (Map 2c) EMDB-49152: Intermembrane lipid transport complex LetAB from Escherichia coli (Composite Map 2) |
| Chemicals | ![]() ChemComp-ZN: ![]() ChemComp-PEF: |
| Source |
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Keywords | LIPID TRANSPORT / Lipid transporter / Outer membrane integrity / MCE system / Metal-binding protein / Intermembrane complex |
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