| Institution: | 1. Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ UK;2. Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK;3. Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17165 Solna, Sweden
Department of Biology, University of Copenhagen, Copenhagen N, 2200 Denmark;4. OMass Therapeutics, The Oxford Science Park, The Schrödinger Building, Kidlington, OX4 4GE UK;5. Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17165 Solna, Sweden;6. Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden;7. Biomolecular Interaction Centre and School of Physical and Chemical Sciences, University of Canterbury, Christchurch, 8140 New Zealand |
| Abstract: | Membrane proteins engage in a variety of contacts with their surrounding lipids, but distinguishing between specifically bound lipids, and non-specific, annular interactions is a challenging problem. Applying native mass spectrometry to three membrane protein complexes with different lipid-binding properties, we explore the ability of detergents to compete with lipids bound in different environments. We show that lipids in annular positions on the presenilin homologue protease are subject to constant exchange with detergent. By contrast, detergent-resistant lipids bound at the dimer interface in the leucine transporter show decreased koff rates in molecular dynamics simulations. Turning to the lipid flippase MurJ, we find that addition of the natural substrate lipid-II results in the formation of a 1:1 protein–lipid complex, where the lipid cannot be displaced by detergent from the highly protected active site. In summary, we distinguish annular from non-annular lipids based on their exchange rates in solution. |
