Lipids modulate the conformational dynamics of a secondary multidrug transporter

Abstract

Direct interactions with lipids have emerged as key determinants of the folding, structure and function of membrane proteins, but an understanding of how lipids modulate protein dynamics is still lacking. Here, we systematically explored the effects of lipids on the conformational dynamics of the proton-powered, multidrug transporter LmrP from Lactococcus lactis utilizing the pattern of distances between spin label pairs previously shown to fingerprint alternating access of the protein. We uncover at the molecular level how the lipid headgroups shape the conformational energy landscape of the transporter. The model emerging from our data hypothesizes a direct interaction between lipid headgroups and a conserved motif of charged residues that control the conformational equilibrium through an interplay of electrostatic interactions within the protein. Together, our data lay the foundation for a comprehensive model of secondary multidrug transport in lipid bilayers.

Alternating access mechanisms of LeuT-fold transporters: trailblazing towards the promised energy landscapes

“…Although not yet explicitly tested, lipids are also likely to modulate this conformational equilibrium. Recent spectroscopic analysis of the proton-dependent multidrug transporter LmrP uncovered shifts in the free energy landscape between inward- and outward-facing conformations that were dependent on lipid headgroup interaction with a conserved charge-relay network [45]. The observation of bound cholesterol in DAT crystal structures [17] to stabilize an outward-facing state that promotes inhibitor binding [46] supports the notion of potential lipid effects on the conformation of LeuT-fold transporters.…”

Structural and Functional Basis for Lipid Synergy on the Activity of the Antibacterial Peptide ABC Transporter McjD

“…We can speculate that the PG stabilizes the transporter in the nucleotide-bound outward occluded state in addition to the reported salt bridges (13); the lipid is found between TM3 and 4 that are part of the bundle of helices that undergo conformational changes during the transport cycle. Lipids are known to modulate the structure of membrane proteins and for their role in stabilizing a given conformational state (29,30 , namely A-D). In the low calcium affinity state E2, PE lipids occupy sites A and B, where lipids in site A have been proposed to stabilize this state by keeping TM2 and 4 apart.…”

Nanodiscs in Membrane Biochemistry and Biophysics

“…198 In order to study the effect of various lipids on the conformation and dynamics of multidrug pump LmrP it was assembled in Nanodiscs with PE with a varied degree of methylation of the amino group, specifically DOPE (no methylation), DOPE(Me) 2 (two meth-ylations) and DOPC (fully methylated) and with constant fractions of DOPG (23%) and cardiolipin (10%) in a E.coli polar lipid extract. 199 …”