Key result
The proline-rich domain of S. pombe Wsp1 binds actin filaments with micromolar affinity and slows the rate of actin filament elongation by Mg-ATP-actin monomers by half.
Why the study?
The proline-rich domain of WASp contributes to branching nucleation but was overlooked until the budding yeast Las17 PRD was shown to bind actin filaments.
The proline-rich domains of WASp-family proteins bind actin filaments with micromolar affinity and slow the rate of actin filament elongation, contributing to the stimulation of actin filament branching by the Arp2/3 complex.
Answers are grounded in this paper and cite their sources.
In vitro actin modulation by Wsp1 PRD; leaves open its physiological role in cytoskeletal dynamics.
Background The Wiskott-Aldrich Syndrome protein (WASp) family of proteins plays a crucial role in the activation of the Arp2/3 (actin-related protein 2/3) complex to promote the branching of actin filaments. The proline-rich domain (PRD) of WASp is known to contribute to branching nucleation but was overlooked, until experiments showed that the PRD of budding yeast Las17 can bind actin filaments (1). Methods We purified recombinant proline-rich domains from fission yeast S. pombe Wsp1 and budding yeast S. cerevisiae Las17 to test in biochemical assays of actin binding and polymerization. Results The PRD of the S. pombe Wsp1 binds actin filaments with micromolar affinity. The PRDs of both Wsp1 and Las17 slowed the rate of actin filament elongation by Mg-ATP-actin monomers by half and slowed the spontaneous polymerization of Mg-ATP-actin monomers modestly. Conclusion The affinity of PRDs of WASp-family proteins for actin filaments is high enough to contribute to the reported stimulation of actin filament branching by Arp2/3 complex.
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Rosenbloom et al. (2022) studied this question. Wsp1p-PRD and Las17-PRD was evaluated on Actin filament binding affinity and polymerization rate. The proline-rich domain of S. pombe Wsp1 binds actin filaments with micromolar affinity and slows the rate of actin filament elongation by Mg-ATP-actin monomers by half.
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