Dr. Chloe Martens
Chemistry
King's College
London, UK

Tuesday, September 25, 2018
3:00 pm (CT)
3169 Beckman Institute

Abstract

A growing number of studies report lipids interacting with membrane proteins to modulate their folding, stability and function, yet the molecular details underpinning such processes remain elusive. This is even more pertinent for transporters, which despite being an important class of drug targets lack characterization at molecular level. Here, we combine hydrogen-deuterium exchange mass spectrometry (HDX- MS) with molecular dynamics (MD) simulations to understand how lipids regulate the conformational dynamics of secondary transporters at the molecular level. Using the homologous transporters XylE, LacY and GlpT from Escherichia coli as model systems, we reveal that specific protein-lipid interactions modulate the conformational equilibrium between outward- and inward- facing conformations. We first identify the structural elements involved in the conformational transition between different states by combining state-of-the-art hydrogen deuterium exchange mass spectrometry (HDX-MS) with systematic mutagenesis. We then use tunable nanodiscs and MD simulations to uncover how specific lipids directly modulate such transition. We found that this modulation arises from interactions between the phopspholipid headgroup and a specific network of residues shown through our work to control conformation. This network is highly conserved across homologous transporters and previous biochemical characterization demonstrated that its integrity is an absolute requirement for function. Together, our data provides novel insights into the role of lipids in molecular mechanisms and lay the foundation for a comprehensive model of secondary transport in lipid bilayers