title: Crystalline protein domains and lipid bilayer vesicle shape transformations.
abstract: Cellular membranes can take on a variety of shapes to assist biological processes including endocytosis. Membrane-associated protein domains provide a possible mechanism for determining membrane curvature. We study the effect of tethered streptavidin protein crystals on the curvature of giant unilamellar vesicles (GUVs) using confocal, fluorescence, and differential interference contrast microscopy. Above a critical protein concentration, streptavidin domains align and percolate as they form, deforming GUVs into prolate spheroidal shapes in a size-dependent fashion. We propose a mechanism for this shape transformation based on domain growth and jamming. Osmotic deflation of streptavidin-coated GUVs reveals that the relatively rigid streptavidin protein domains resist membrane bending. Moreover, in contrast to highly curved protein domains that facilitate membrane budding, the relatively flat streptavidin domains prevent membrane budding under high osmotic stress. Thus, crystalline streptavidin domains are shown to have a stabilizing effect on lipid membranes. Our study gives insight into the mechanism for protein-mediated stabilization of cellular membranes.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. mhorton@mit.edu
authors.forename: Margaret R
authors.initials: MR
authors.lastname: Horton
authors.forename: Suliana
authors.initials: S
authors.lastname: Manley
authors.forename: Silvana R
authors.initials: SR
authors.lastname: Arevalo
authors.forename: Alexander E
authors.initials: AE
authors.lastname: Lobkovsky
authors.forename: Alice P
authors.initials: AP
authors.lastname: Gast
mesh_terms: D001360:Avidin / Q000737:chemistry; D001703:Biophysics / Q000379:methods*; D019921:Biotinylation; D002627:Chemistry, Physical / Q000379:methods*; D003460:Crystallization; D008051:Lipid Bilayers; D008055:Lipids / Q000737:chemistry; D008856:Microscopy, Fluorescence; D009995:Osmosis; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D019809:Streptavidin / Q000737:chemistry
chemical_list: D008051:Lipid Bilayers; D008055:Lipids; D011506:Proteins; D001360:Avidin; D019809:Streptavidin