Abstract
Nucleation of branched actin filaments by Arp2/3 complex is tightly regulated to control actin assembly in cells. Arp2/3 complex activation involves conformational changes brought about by ATP, Nucleation Promoting Factor (NPF) proteins, actin filaments and NPF-recruited actin monomers. To understand how these factors promote activation, we must first understand how the complex is held inactive in their absence. Here we demonstrate that the Arp3 C-terminal tail is a structural switch that prevents Arp2/3 complex from adopting an active conformation. The interaction between the tail and a hydrophobic groove in Arp3 blocks movement of Arp2 and Arp3 into an activated filament-like (short pitch) conformation. Our data indicate ATP binding destabilizes this interaction via an allosteric link between the Arp3 nucleotide cleft and the hydrophobic groove, thereby promoting the short-pitch conformation. Our results help explain how Arp2/3 complex is locked in an inactive state without activators and how autoinhibition is relieved.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Actin Cytoskeleton / metabolism*
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Actin-Related Protein 2 / genetics
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Actin-Related Protein 2 / metabolism*
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Actin-Related Protein 2-3 Complex / chemistry
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Actin-Related Protein 2-3 Complex / genetics
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Actin-Related Protein 2-3 Complex / metabolism*
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Actin-Related Protein 3 / genetics
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Actin-Related Protein 3 / metabolism
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Adenosine Triphosphate / metabolism*
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Amino Acid Sequence
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Conserved Sequence
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Protein Conformation
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Protein Multimerization
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Protein Stability
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
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Schizosaccharomyces / genetics
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Schizosaccharomyces / metabolism
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Schizosaccharomyces pombe Proteins / genetics
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Schizosaccharomyces pombe Proteins / metabolism*
Substances
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ARP2 protein, S cerevisiae
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ARP3 protein, S cerevisiae
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Actin-Related Protein 2
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Actin-Related Protein 2-3 Complex
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Actin-Related Protein 3
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Saccharomyces cerevisiae Proteins
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Schizosaccharomyces pombe Proteins
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Adenosine Triphosphate