Screening the Sensing of Membrane Curvature by BAR domains on Single Liposome Arrays

Membrane traffic relies on the preferential binding of protein domains to high curvature areas. The BAR domain is a banana shaped α-helical homodimer found in several proteins families that play a major role in endocytosis, actin regulation and signaling.[1] It is shown to sense and/or induce lipid membrane curvature by peripheral binding. While most attention have been aimed at curvature induction[2], we investigate the molecular mechanism of curvature sensing by performing a thorough study on the whole superfamily of BAR domain proteins including NBARs, FBARs, IBARs. We compared the sensing properties of 9 different BAR proteins and also measured on numerous truncation or point mutation variants.We developed a high-throughput single liposome assay[3] to test the curvature dependent binding properties of these BAR proteins. Fluorescence intensities of immobilized vesicles allowed us to measure accurately their size/curvature and the respective densities of BAR proteins. Combining selectivity curves with the mutagenesis studies enabled us to evaluate the contribution of dimer structure, electrostatics and helix insertion to membrane curvature sensing by BAR domain proteins.Our results prompt a thorough reevaluation of the membrane curvature sensing mechanism of BAR domain proteins.[1] McMahon, H. T. & Gallop, J. L. Membrane curvature and mechanisms of dynamic cell membrane remodelling. Nature 438, 590-596 (2005).[2] Frost A. et al. Structural Basis of Membrane Invagination by F-BAR domains, Cell, 132, 807-817 (2008).[3] Stamou, D., Duschl, C., Delamarche, E. & Vogel, H. Self-assembled microarrays of attoliter molecular vessels. Angewandte Chemie-International Edition, Cover Page Article 42, 5580-5583 (2003).