Pozza, A. | bioRxiv Science

bioRxiv2025

Atomic scale description of the allosteric coupling between a lipid bilayer and a membrane protein

Biological membranes are complex environments whose functions are closely tied to the dynamic interactions between lipids and proteins. Here, we utilize high-pressure NMR of lipid nanodiscs paired with molecular dynamics simulations to elucidate at the atomic scale the allosteric dialog between the lipid bilayer and a bacterial model membrane protein, OmpX. We discover that OmpX delays the gelation process by liquefying the annular shell of lipids through hydrophobic and roughness matching processes at the protein surface. Furthermore, the alteration of the mechanical properties of the lipid bilayer directly impacts the energy landscape of amino acid side chains at the lipid/protein interface, but also, unexpectedly, at the protein core. Our work highlights a potential thermodynamically coupled but kinetically uncoupled allosteric pathway linking lipid dynamics with the interior of membrane proteins, directly impacting our understanding of membrane function. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/634742v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@5c02ddorg.highwire.dtl.DTLVardef@c033c5org.highwire.dtl.DTLVardef@86f90forg.highwire.dtl.DTLVardef@149480e_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2024

Biochemical, biophysical, and structural investigations of two mutants (C154Y and R312H) of the human Kir2.1 channel involved in the Andersen-Tawil syndrome.

Inwardly rectifying potassium (Kir) channels play a pivotal role in physiology by establishing, maintaining, and regulating the resting membrane potential of the cells, particularly contributing to the cellular repolarization of many excitable cells. Dysfunction in Kir2.1 channels is implicated in several chronic and debilitating human diseases for which there are currently no effective treatments. Specifically, Kir2.1-R312H and Kir2.1-C154Y mutations are associated with Andersen-Tawil syndrome (ATS) in humans. We have investigated the impact of these two mutants in the trafficking of the channel to the cell membrane and function in Xenopus laevis oocytes. Despite both mutations being successfully trafficked to the cell membrane and capable of binding PIP2 (phosphatidylinositol-4,5- bisphosphate), the main modulator for channel activity, they resulted in defective channels that do not display K+ current, albeit through different molecular mechanisms. Co-expression studies showed that R312H and C154Y are expressed and associated with the WT subunits. While WT subunits could rescue R312H dysfunction, the presence of a unique C154Y subunit disrupts the function of the entire complex, which is a typical feature of mutations with a dominant-negative effect. Molecular dynamics simulations showed that Kir2.1-C154Y mutation induces a loss in the structural plasticity of the selectivity filter, impairing the K+ flow. In addition, the cryo-EM structure of the Kir2.1-R312H mutant has been reconstructed. This study identified the molecular mechanisms by which two ATS-causing mutations impact Kir2.1 channel function and provide valuable insights that can guide potential strategies for the development of future therapeutic interventions for ATS.

biophysics↗