The Arp2/3 complex is critical for nucleation and crosslinking of actin filaments. To gain insight into its subunit topology and assembly pathway, we systematically examined interactions among subunits of human Arp2/3 complex by yeast two-hybrid assays. It was shown that p20-Arc was able to interact with p21-Arc, p34-Arc, and p16-Arc, respectively. In contrast, p41-Arc only interacted with p20-Arc/p16-Arc heterodimer. In addition, we found that structural integrity was important for association between p20-Arc and p21-Arc, while the N-terminal half of p34-Arc was dispensable for its binding to p20-Arc. Our data suggest a key role of p20-Arc and a multistep pathway for the complex formation.
Copyright 2001 Academic Press.