title: Annealing accounts for the length of actin filaments formed by spontaneous polymerization.
abstract: We measured the lengths of actin filaments formed by spontaneous polymerization of highly purified actin monomers by fluorescence microscopy after labeling with rhodamine-phalloidin. The length distributions are exponential with a mean of approximately 7 microm (2600 subunits). This length is independent of the initial concentration of actin monomer, an observation inconsistent with a simple nucleation-elongation mechanism. However, with the addition of physically reasonable rates of filament annealing and fragmenting, a nucleation-elongation mechanism can reproduce the observed average length of filaments in two types of experiments: 1) filaments formed from a wide range of highly purified actin monomer concentrations, and 2) filaments formed from 24 microM actin over a range of CapZ concentrations.
authors.affiliation: Department of Chemistry and Biochemistry, University of California-San Diego, La Jolla, California 92093-0365, USA. dsept@ucsd.edu
authors.forename: D
authors.initials: D
authors.lastname: Sept
authors.forename: J
authors.initials: J
authors.lastname: Xu
authors.forename: T D
authors.initials: TD
authors.lastname: Pollard
authors.forename: J A
authors.initials: JA
authors.lastname: McCammon
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000302:isolation & purification / Q000648:ultrastructure; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D001704:Biopolymers / Q000737:chemistry / Q000302:isolation & purification; D066298:In Vitro Techniques; D008856:Microscopy, Fluorescence; D008956:Models, Chemical; D010590:Phalloidine; D011817:Rabbits; D012235:Rhodamines
chemical_list: D000199:Actins; D001704:Biopolymers; D012235:Rhodamines; D010590:Phalloidine