Affiliation: | 1. Department of Structural Biology, Weizmann Institute of Science, Herzl St. 234, 7610001 Rehovot, Israel These authors contributed equally to this work.;2. Centre for Structural Systems Biology (CSSB), DESY and European Molecular Biology Laboratory Hamburg, Notkestrasse 85, 22607 Hamburg, Germany These authors contributed equally to this work.;3. Department of Chemical and Biological Physics, Weizmann Institute of Science, Herzl St. 234, 7610001 Rehovot, Israel;4. Department of Structural Biology, Weizmann Institute of Science, Herzl St. 234, 7610001 Rehovot, Israel;5. Centre for Structural Systems Biology (CSSB), DESY and European Molecular Biology Laboratory Hamburg, Notkestrasse 85, 22607 Hamburg, Germany |
Abstract: | Membrane proteins require lipid bilayers for function. While lipid compositions reach enormous complexities, high-resolution structures are usually obtained in artificial detergents. To understand whether and how lipids guide membrane protein function, we use single-molecule FRET to probe the dynamics of DtpA, a member of the proton-coupled oligopeptide transporter (POT) family, in various lipid environments. We show that detergents trap DtpA in a dynamic ensemble with cytoplasmic opening. Only reconstitutions in more native environments restore cooperativity, allowing an opening to the extracellular side and a sampling of all relevant states. Bilayer compositions tune the abundance of these states. A novel state with an extreme cytoplasmic opening is accessible in bilayers with anionic head groups. Hence, chemical diversity of membranes translates into structural diversity, with the current POT structures only sampling a portion of the full structural space. |