A vast body of evidence coming from different microscopy techniques has been instrumental in concluding the long debate on whether biological membranes presented lateral segregation of proteins and lipids. Currently, the existence of membrane domains in both eukaryotes and prokaryotes is common ground. However, the mechanisms that sustain membrane domain formation and maintenance remain largely unknown. Our work is focus on the study of eisosomes, recently discovered plasma membrane domains in S. cerevisiae. We showed that Pil1 and Lsp1, the major proteinaceous components of eisosomes, are able to form self-assemblies that bind and curve membranes both in vivo and in vitro. We also showed that Lsp1 and Pil1 membrane-sculpting abilities are associated with the generation and organization of membrane domains (1,2). Thus, our current work supports the hypothesis that a mechanism for membrane eisosome domain formation is membrane curvature generation directed by Pil1-Lsp1 assemblies. To address this hypothesis we are applying Fluorescence Correlation Spectroscopy and Number and Brightness Analysis to describe the dynamics of Pil1 and Lsp1 in vivo. We are studying the oligomeric state and concentration of these proteins in the cytoplasm soluble fraction and in the plasma membrane. Also we plan to study the kinetic parameters of Pil1, Lsp1 and plasma membrane interactions during eisosome biogenesis and also during stationary phase.References1. Olivera-Couto A, Grana M, Harispe L, Aguilar PS (2011) The eisosome core is composed of BAR domain proteins. Mol Biol Cell 22: 2360-2372.2. Olivera-Couto A, Aguilar PS (2012) Eisosomes and plasma membrane organization. Molecular Genetics and Genomics 287(8): 607-20.