Insights into the influence of nucleotides on actin family proteins from seven structures of Arp2/3 complex.
ATP is required for nucleation of actin filament branches by Arp2/3 complex, but the influence of ATP binding and hydrolysis are poorly understood. We determined crystal structures of bovine Arp2/3 complex cocrystallized with various bound adenine nucleotides and cations. Nucleotide binding favors closure of the nucleotide-binding cleft of Arp3, but no large-scale conformational changes in the complex. Thus, ATP binding does not directly activate Arp2/3 complex but is part of a network of interactions that contribute to nucleation. We compared nucleotide-induced conformational changes of residues lining the cleft in Arp3 and actin structures to construct a movie depicting the proposed ATPase cycle for the actin family. Chemical crosslinking stabilized subdomain 1 of Arp2, revealing new electron density for 69 residues in this subdomain. Steric clashes with Arp3 appear to be responsible for intrinsic disorder of subdomains 1 and 2 of Arp2 in inactive Arp2/3 complex.
Nolen
Brad J
BJ
Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA.
Pollard
Thomas D
TD
D008841:Actin Cytoskeleton; D051376:Actin-Related Protein 2-3 Complex / Q000737:chemistry* / Q000378:metabolism*; D000199:Actins / Q000737:chemistry* / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000737:chemistry / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003432:Cross-Linking Reagents / Q000737:chemistry; D005976:Glutaral / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary
D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D003432:Cross-Linking Reagents; D046911:Macromolecular Substances; D009711:Nucleotides; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D005976:Glutaral