Plays a role in the organization of the actin cytoskeleton. May function as ATP-binding component of the Arp2/3 complex which is involved in regulation of actin polymerization and together with an activating nucleation-promoting factor (NPF) mediates the formation of branched actin networks. May decrease the metastatic potential of tumors. Interacts with the Arp2/3 complex composed of ARP2, ARP3, ARPC1B, ARPC1B/p41-ARC, ARPC2/p34-ARC, ARPC3/p21-ARC, ARPC4/p20-ARC and ARPC5/p16-ARC. Detected in fetal brain. Detected throughout the adult brain, in neurons from gray matter, but not in white matter. Detected in liver, skeletal muscle and pancreas. Detected in lung adenocarcinoma cells with low metastatic potential, but not in lung adenocarcinoma cells with high metastatic potential. Belongs to the actin family. ARP3 subfamily.