title: Crystal structure of Arp2/3 complex.
abstract: We determined a crystal structure of bovine Arp2/3 complex, an assembly of seven proteins that initiates actin polymerization in eukaryotic cells, at 2.0 angstrom resolution. Actin-related protein 2 (Arp2) and Arp3 are folded like actin, with distinctive surface features. Subunits ARPC2 p34 and ARPC4 p20 in the core of the complex associate through long carboxyl-terminal alpha helices and have similarly folded amino-terminal alpha/beta domains. ARPC1 p40 is a seven-blade beta propeller with an insertion that may associate with the side of an actin filament. ARPC3 p21 and ARPC5 p16 are globular alpha-helical subunits. We predict that WASp/Scar proteins activate Arp2/3 complex by bringing Arp2 into proximity with Arp3 for nucleation of a branch on the side of a preexisting actin filament.
authors.affiliation: Structural Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Robinson
authors.forename: K
authors.initials: K
authors.lastname: Turbedsky
authors.forename: D A
authors.initials: DA
authors.lastname: Kaiser
authors.forename: J B
authors.initials: JB
authors.lastname: Marchand
authors.forename: H N
authors.initials: HN
authors.lastname: Higgs
authors.forename: S
authors.initials: S
authors.lastname: Choe
authors.forename: T D
authors.initials: TD
authors.lastname: Pollard
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000378:metabolism*; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000737:chemistry* / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D018360:Crystallography, X-Ray; D003598:Cytoskeletal Proteins; D046911:Macromolecular Substances; D008954:Models, Biological; D008958:Models, Molecular; D018482:Muscle, Skeletal; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D055672:Static Electricity; D013950:Thymus Gland
chemical_list: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D003598:Cytoskeletal Proteins; D046911:Macromolecular Substances; D021122:Protein Subunits; D000255:Adenosine Triphosphate