title: Pathway of actin filament branch formation by Arp2/3 complex.
abstract: A spectroscopic assay using pyrene-labeled fission yeast Arp2/3 complex revealed that the complex binds to and dissociates from actin filaments extremely slowly with or without the nucleation-promoting factor fission yeast Wsp1-VCA. Wsp1-VCA binds both Arp2/3 complex and actin monomers with high affinity. These two ligands have only modest impacts on the interaction of the other ligand with VCA. Simulations of a mathematical model based on the kinetic parameters determined in this study and elsewhere account for the full time course of actin polymerization in the presence of Arp2/3 complex and Wsp1-VCA and show that an activation step, postulated to follow binding of a ternary complex of Arp2/3 complex, a bound nucleation-promoting factor, and an actin monomer to an actin filament, has a rate constant at least 0.15 s(-1). Kinetic parameters determined in this study constrain the process of actin filament branch formation during cellular motility to one main pathway.
authors.affiliation: Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA.
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Beltzner
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Pollard
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism*; D000199:Actins / Q000737:chemistry* / Q000494:pharmacology; D005454:Fluorescence Polarization; D031541:Fluorescence Resonance Energy Transfer; D007700:Kinetics; D008024:Ligands; D013058:Mass Spectrometry; D008954:Models, Biological; D008962:Models, Theoretical; D008968:Molecular Conformation; D016296:Mutagenesis; D011485:Protein Binding; D012568:Schizosaccharomyces / Q000502:physiology*; D013053:Spectrophotometry / Q000379:methods; D013997:Time Factors
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D008024:Ligands