Component of the SWR1 complex which mediates the ATP-dependent exchange of histone H2A for the H2A variant HZT1 leading to transcriptional regulation of selected genes by chromatin remodeling. Involved in chromosome stability. Component of the SWR1 chromatin remodeling complex composed of at least ACT1, ARP4, RVB1, RVB2, ARP6, YAF9, VPS71, VPS72, SWC3, SWC4, SWC5, SWC7 and SWR1, and perhaps BDF1. Present with 238 molecules/cell in log phase SD medium. Belongs to the actin family. ARP6 subfamily.