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Nat Cell Biol. 2001 Jan;3(1):76-82.

Interaction of WASP/Scar proteins with actin and vertebrate Arp2/3 complex.

Author information

1
Structural Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, USA.

Abstract

The Wiskott-Aldrich-syndrome protein (WASP) regulates polymerization of actin by the Arp2/3 complex. Here we show, using fluorescence anisotropy assays, that the carboxy-terminal WA domain of WASP binds to a single actin monomer with a Kd of 0.6 microM in an equilibrium with rapid exchange rates. Both WH-2 and CA sequences contribute to actin binding. A favourable DeltaH of -10 kcal mol(-1) drives binding. The WA domain binds to the Arp2/3 complex with a Kd of 0.9 microM; both the C and A sequences contribute to binding to the Arp2/3 complex. Wiskott-Aldrich-syndrome mutations in the WA domain that alter nucleation by the Arp2/3 complex over a tenfold range without affecting affinity for actin or the Arp2/3 complex indicate that there may be an activation step in the nucleation pathway. Actin filaments stimulate nucleation by producing a fivefold increase in the affinity of WASP-WA for the Arp2/3 complex.

PMID:
11146629
DOI:
10.1038/35050590
[Indexed for MEDLINE]

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