Lateral membrane compartments: Formation, functional relevance and genomics

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Evidence is accumulating that the Singer/Nicholson model of fluid mosaic membranes may have to be modified. Membranes, especially the plasma membrane, seem to be laterally subcompartmented. In Saccharomyces cerevisiae two compartments have been distinguished by confocal laser scanning microscopy: one is enriched in several proton/substrate symporters as well as in ergosterol, the other one houses the plasma membrane H+-ATPase. Recently, we have demonstrated that the membrane potential influences the compartmentation pattern of some of these proteins. – The following investigations are planned for the next two years: A) Protein clustering shall be looked for by applying EM/immuno-gold detection. B) The protein mobility in the various domains will be studied. C) The yeast deletion collection will be screened for mutants, in which the distribution of GFP-fusion proteins – normally forming distinct patterns – will be disturbed. D) Functional investigations: a)Transport kinetics of symporters homogenously present in the membrane (from the mutant screen) will be compared with wild type cells, where they form the typical patchy pattern. b) The relation of the symporter compartment to the so-called “eisosomes” (Walther et al, 2006) will be tested to see, whether membrane compartmentation is related to endocytosis and protein turnover.