Interaction at the membrane midplane mediates interleaflet coupling

Description

Interaction at the membrane midplane mediates interleaflet coupling Andreas Horner, Sergey Akimov, Yuri N. Antoneko, and Peter Pohl Interleaflet coupling is important for the formation of rafts or other signaling platforms in biological membranes. If membrane proteins are involved, the transmembrane cluster does not form by registration of half-clusters from the individual leaflets but the components from different leaflets first align forming a nucleus, which in a second step develops into a cluster by the concerted recruitment of more constituents from both leaflets (Antonenko et al. 2012). Coupling in pure lipids is less clear. Here we investigate the role of lipid interdigidation as a coupling mechanism. To contribute, the “bottoms” of longer and shorter than average acyl chains must experience different frictions. Since only the longer chains are in contact with molecules in the opposing monolayer, they are exposed to a larger velocity gradient than the shorter ones. To dissect this so-called interlayer viscosity from the frictional drag on the side surface of a diffusing lipid molecule, we induced small lipid clusters in a freestanding planar bilayer by polymer adsorption. Fluorescence correlation spectroscopy measurements revealed a larger mobility drop for the lipids in direct contact with the polymer than for those in the distant monolayer. From the slide of the lipid patches in both monolayers against each other we obtained the same value of 3x109 Js m-4 for the interlayer viscosity of both short and long lipid analogues (12 and 18 C atoms). This observation rules out lipid interdigitation as a coupling mechanism.

Period	17 Jul 2013
Event title	European Biophysics Conference 2013, Lissabon Portugal
Event type	Conference
Location	PortugalShow on map