title: Intriguing self-assembly of large granules of F-actin facilitated by gelsolin and alpha-actinin.
abstract: We report microscopic observations and a structural determination of actin granules self-assembled in concentrated solutions of actin filaments (F-actin). Optical microscopy shows reproducible formation of numerous and stable granules of densely packed F-actin of variable sizes on the order of 10 microm. These granules coexist with a uniform network of F-actin of a lower concentration. The microscopic segregation of F-actin into two distinct states is assisted by an actin cross-linking protein, alpha-actinin. The rapid on and off rates and temperature sensitivity of the alpha-actinin/F-actin interaction facilitate the formation of multi-micrometer-sized granules of well-defined shapes. Additional physical factors such as the excluded volume effect and the minimization of surface energy act in concert with the specific molecular interactions to define the intriguing granular formation. Both the biochemical specificity of alpha-actinin and the thermodynamics of phase transitions are required for understanding such large scale self-assembly.
authors.affiliation: Physics Department, Brown University, 184 Hope Street, Providence, Rhode Island 02912, USA. Jay_Tang@Brown.edu
authors.forename: Jay X
authors.initials: JX
authors.lastname: Tang
authors.forename: Hyeran
authors.initials: H
authors.lastname: Kang
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Jia
mesh_terms: D000185:Actinin / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D018260:Gelsolin / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D011485:Protein Binding; D011817:Rabbits
chemical_list: D018260:Gelsolin; D000185:Actinin