[Plasma membrane--order or chaos?].

In the influential "fluid mosaic" model of plasmalemma, transmembrane proteins drift regardless of lipids. Recently researches widen this to a view in which membrane lipids are not randomly distributed but they form liquid-ordered regions with local heterogenity, called lipid rafts. Lipid rafts are subdomains of the plaSma membrane that contain high concentration of cholesterol and glycosphingolipids. They are 50-100 nm distinct liquid-ordered regions of the membrane that are resistant to extraction with nonionic detergents. They are proposed to function as dynamic lipid assemblies which serve as platforms for protein segregation and signaling, protein and lipid sorting during post-Golgi sorting, dynamic of plasmalemma and virial entry budding. Markers for the lipid rafts are flotillin, GPI - linked proteins, Src family kinases, EGF receptors and G proteins. The lifetime, biological relevance and properties of these domains in vivo are still unclear. However the answers will shape our views of signaling and membrane dynamics.