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Selectivity of membrane proteins toward individual phospholipids

Vendredi 20 juin 2014 11:00 - Duree : 1 heure
Lieu : Salle des séminaires de l’IBS - 6 rue Jules Horowitz - Grenoble

Orateur : Arthur LAGANOWSKY (University of Oxford, United Kingdom)

The folding, structure, and function of membrane proteins are often influenced by their surrounding lipid environment. Membrane protein lipid interactions are of fundamental biological importance and a number of key questions remain. As a step towards understanding theseinteractions we have developed a mass spectrometry (MS) approach to monitor the effects of individual lipid binding events on three membrane protein complexes anticipated to respond differently to the phospholipid environment : the mechanosensitive channel, aquaporin Z, and the ammonia channel. Using ion mobility (IM)-MS we resolve individual phospholipid-bound states of membrane proteins, in folded conformations, devoid of the complication of the lipid bilayer. We then rank bound phospholipids based on their ability to prevent gas-phase unfolding. Combining our IM-MS data for the three protein complexes with molecular dynamic (MD) simulations we identify probable lipid binding sites. Phosphatidylglycerol, identified here as significantly stabilizing the ammonium channel, prompted us to determine its crystal structure in this lipid environment. The 2.3Å resolution structure reveals bound lipids in one of the sites predicted by IM-MS and, by comparison with previous structures, distinct conformational changes induced by phospholipid binding that reposition residues to interact with the phospholipid bilayer. Overall our results allow us to conclude that resistance to unfolding correlates directly with specific lipid-binding events that not only modulate membrane protein stability but may also induce conformational change. More widely we anticipate that this approach will enable the important distinction between small molecules that merely bind from those that also stabilize, consequently revealing the effects of lipid, drug or cofactor binding on membrane protein structure and function.

Contact : odile.kaikati@ibs.fr

Discipline évènement : (Biologie / Chimie)
Entité organisatrice : (IBS)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire IBS)
Site de l'évènement : Polygone scientifique

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