The Arp2/3 complex creates filament branches leading to an enhancement in the rate of actin polymerization. Work with Arp complexes from different sources indicated that it was inactive by itself, required an activating factor such as WASP, and might exhibit a preference for ATP or ADP-Pi actin. However, with yeast actin, Pi release is almost concurrent with polymerization eliminating the presence of an ADP-Pi cap. We thus investigated the ability of yeast Arp2/3 complex (yArp2/3) to facilitate yeast actin polymerization in the presence and absence of the Arp2/3-activating factor Las17p WA. yArp2/3 significantly accelerates yeast actin, but not muscle actin, polymerization in the absence of Las17p WA. Addition of Las17p WA further enhances yeast actin polymerization by yArp2/3 and allows the complex to now assist muscle actin polymerization. This actin isoform difference is not observed with bovine Arp2/3 complex, since the N-WASP VCA fragment is required for polymerization of both actins. Observation of individual branching filaments showed that Las17p WA increased the persistence of filament branches. Compared with WT actin, V159N mutant actin, proposed to be more ATP-like in behavior, exhibited an enhanced rate of polymerization in the presence of yArp2/3 complex. yArp2/3 caused a significant rate of Pi release prior to observation of an increase in filament mass but while branched structures were present. Thus, yeast F-actin can serve as a primary yArp2/3 activating factor indicating that a newly formed yeast actin filament has a topology, unlike that of muscle actin, that is recognized specifically by yArp2/3.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|