| The human complex consists of seven subunits which include the actin related proteins Arp 2 and Arp 3 , and five others referred to as p 41 Arc , p 34 Arc , p 21 Arc , p 20 Arc , and p 16 Arc ( p omplex ) . ^^^ Human Arp 2 and Arp 3 are very similar to family members from other species . p 41 Arc is a new member of the Sop 2 family of WD ( tryptophan and aspartate ) repeat containing proteins and may be posttranslationally modified , suggesting that it may be involved in regulating the activity and / or localization of the complex . p 34 Arc , p 21 Arc , p 20 Arc , and p 16 Arc define novel protein families . ^^^ |