title: Actin assembly at model-supported lipid bilayers.
abstract: We report on the use of supported lipid bilayers to reveal dynamics of actin polymerization from a nonpolymerizing subphase via cationic phospholipids. Using varying fractions of charged lipid, lipid mobility, and buffer conditions, we show that dynamics at the nanoscale can be used to control the self-assembly of these structures. In the case of fluid-phase lipid bilayers, the actin adsorbs to form a uniform two-dimensional layer with complete surface coverage whereas gel-phase bilayers induce a network of randomly oriented actin filaments, of lower coverage. Reducing the pH increased the polymerization rate, the number of nucleation events, and the total coverage of actin. A model of the adsorption/diffusion process is developed to provide a description of the experimental data and shows that, in the case of fluid-phase bilayers, polymerization arises equally due to the adsorption and diffusion of surface-bound monomers and the addition of monomers directly from the solution phase. In contrast, in the case of gel-phase bilayers, polymerization is dominated by the addition of monomers from solution. In both cases, the filaments are stable for long times even when the G-actin is removed from the supernatant-making this a practical approach for creating stable lipid-actin systems via self-assembly.
authors.affiliation: School of Physics and Astronomy, University of Leeds, Leeds, United Kingdom.
authors.forename: George R
authors.initials: GR
authors.lastname: Heath
authors.forename: Benjamin R G
authors.initials: BR
authors.lastname: Johnson
authors.forename: Peter D
authors.initials: PD
authors.lastname: Olmsted
authors.forename: Simon D
authors.initials: SD
authors.lastname: Connell
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Evans
mesh_terms: D000199:Actins / Q000737:chemistry*; D000327:Adsorption; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D057054:Molecular Imaging; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D011817:Rabbits
chemical_list: D000199:Actins; D008051:Lipid Bilayers