title: Reconstitution of human Arp2/3 complex reveals critical roles of individual subunits in complex structure and activity.
abstract: The Arp2/3 complex is a seven-protein assembly that is critical for actin nucleation and branching in cells. Here we report the reconstitution of active human Arp2/3 complex after expression of all seven subunits in insect cells. Expression of partial complexes revealed that a heterodimer of the p34 and p20 subunits constitutes a critical structural core of the complex, whereas the remaining subunits are peripherally located. Arp3 is crucial for nucleation, consistent with it being a structural component of the nucleation site. p41, p21, and p16 contribute differently to nucleation and stimulation by ActA and WASP, whereas p34/p20 bind actin filaments and likely function in actin branching. This study reveals that the nucleating and organizing functions of Arp2/3 complex subunits are separable, indicating that these activities may be differentially regulated in cells.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
authors.forename: H
authors.initials: H
authors.lastname: Gournier
authors.forename: E D
authors.initials: ED
authors.lastname: Goley
authors.forename: H
authors.initials: H
authors.lastname: Niederstrasser
authors.forename: T
authors.initials: T
authors.lastname: Trinh
authors.forename: M D
authors.initials: MD
authors.lastname: Welch
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D003598:Cytoskeletal Proteins; D006801:Humans; D046911:Macromolecular Substances; D008954:Models, Biological; D011108:Polymers / Q000737:chemistry; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
chemical_list: C495926:ACTR2 protein, human; C495928:ACTR3 protein, human; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D003598:Cytoskeletal Proteins; D046911:Macromolecular Substances; D011108:Polymers; D021122:Protein Subunits; D011994:Recombinant Proteins