The ability of the plasma membrane to form subcompartments by the generation of microdomains is a wide spread feature throughout all organisms. The spatial separation of various biological processes along the membrane implicates a necessity for correct function and/or regulation. However, despite extensive studies the functional importance of this compartmentation is still not well understood.

In Saccharomyces cerevisiae three lateral distribution patterns of plasma membrane proteins can be observed. While some proteins show a rather homogeneous distribution (e.g. Hxt1, Gap1), proteins as the H+-ATPase Pma1 and associated ones localize to a mesh-like pattern (membrane compartment P, MCP). A third compartment appears in a spotty distribution, housing at least 17 proteins, among which the arginine H+-symporter Can1 was the first one to be described (membrane compartment C, MCC). As MCC is filling the “holes” of MCP, these two compartments are completely separated from each other. Also certain lipids follow this compartmentation. While sterols are shown to accumulate within MCC, experimental findings suggest that MCP may be enriched in sphingolipids.

The domains of MCC are clusters with a diameter of about 200-300 nm. They can easily be visualized by confocal laser scanning microscopy using fluorescence labelled proteins or lipids.

Moreover the compartmentation of various H+-symport proteins is highly dependent on the energization of the membrane. Plasma membrane depolarization causes reversible dispersion of the proteins. This finding suggests a novel role of the membrane potential in the organization of the plasma membrane.

Cover of "Eukaryotic Cell" June 2006.