jz8b00859_si_001.pdf (1.21 MB)
Transmembrane Helix Induces Membrane Fusion through Lipid Binding and Splay
journal contribution
posted on 2018-05-25, 00:00 authored by Holger
A. Scheidt, Katja Kolocaj, Julie Veje Kristensen, Daniel Huster, Dieter LangoschThe fusion of biological
membranes may require splayed lipids whose
tails transiently visit the headgroup region of the bilayer, a scenario
suggested by molecular dynamics simulations. Here, we examined the
lipid splay hypothesis experimentally by relating liposome fusion
and lipid splay induced by model transmembrane domains (TMDs). Our
results reveal that a conformationally flexible transmembrane helix
promotes outer leaflet mixing and lipid splay more strongly than a
conformationally rigid one. The lipid dependence of basal as well
as of TMD-driven lipid mixing and splay suggests that the cone-shaped
phosphatidylethanolamine stimulates basal fusion via enhancing lipid
splay and that the negatively charged phosphatidylserine inhibits
fusion via electrostatic repulsion. Phosphatidylserine also strongly
differentiates basal and helix-driven fusion, which is related to
its preferred interaction with the conformationally more flexible
transmembrane helix. Thus, the contribution of a transmembrane helix
to membrane fusion appears to depend on lipid binding, which results
in lipid splay.