Abstract
We have studied the contributions of stored elastic energies in liquid-ordered (Lo) and liquid-disordered (Ld) domains to transmembrane proteins using the lateral pressure concept. In particular we applied previously reported experimental data for the membrane thickness, intrinsic curvature and bending elasticities of coexisting Lo/Ld domains to calculate whether proteins of simple geometric shapes would preferentially diffuse into Lo or Ld domains and form oligomers of a certain size. For the studied lipid mixture we generally found that proteins with convex shapes prefer sorting to Ld phases and the formation of large clusters. Lo domains in turn would be enriched in monomers of concave shaped proteins. We further observed that proteins which are symmetric with respect to the bilayer center prefer symmetric Lo or Ld domains, while asymmetric proteins favor a location in domains with Lo/Ld asymmetry. In the latter case we additionally retrieved a strong dependence on protein directionality, thus providing a mechanism for transmembrane protein orientation.
Highlights
IntroductionFor several decades lipid-only membranes have served as chemically well-defined mimics of biological membranes enabling detailed physicochemical and biophysical studies of diverse structural and dynamical membrane properties.[1,2,3] One aspect that has ever attracted significant scientific attention is the coupling of membrane properties to protein function
For several decades lipid-only membranes have served as chemically well-defined mimics of biological membranes enabling detailed physicochemical and biophysical studies of diverse structural and dynamical membrane properties.[1,2,3] One aspect that has ever attracted significant scientific attention is the coupling of membrane properties to protein function.in its conformational equilibrium and/or its preferred partitioning into a given lipid environment.Here we focus on membrane-mediated protein-sorting into liquid-ordered (Lo) or liquid-disordered (Ld) domains of flat, tension-free bilayers
Our results demonstrate that the lateral pressure distribution in Lo domains would drive concave proteins towards monomeric forms, while convex proteins in Ld domains would tend to aggregate into large clusters (Fig. 9A)
Summary
For several decades lipid-only membranes have served as chemically well-defined mimics of biological membranes enabling detailed physicochemical and biophysical studies of diverse structural and dynamical membrane properties.[1,2,3] One aspect that has ever attracted significant scientific attention is the coupling of membrane properties to protein function. We focus on membrane-mediated protein-sorting into liquid-ordered (Lo) or liquid-disordered (Ld) domains of flat, tension-free bilayers. It is well-established that cholesterolcontaining mixtures of high-melting and low-melting lipids display Lo/Ld phase coexistence over a broad range of compositions and temperatures.[22,23,24] These systems serve commonly as models for outer plasma membranes that can be studied by an array of biophysical techniques. For example our laboratory has recently reported detailed in situ values for the domains’ structural and elastic properties using small-angle X-ray scattering.[25,26,27]
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