Fig. 6: Model of Arp2/3 complex inhibition by Arpin versus activation by actin—NPF.
From: Molecular mechanism of Arp2/3 complex inhibition by Arpin
Arp2/3 complex is activated by actin—NPF binding to two sites, a high-affinity site-1 on Arp2-ArpC1 and a lower affinity site-2 on Arp37 (Activation, top). Actin-NPF binding to site-1 shifts the equilibrium towards the short-pitch conformation, which also facilitates actin—NPF binding to Arp3. Arpin inhibits Arp2/3 complex activation through a combination of two effects (Inhibition, bottom). By locking the inhibitory tail of Arp320, Arpin inhibits the short-pitch transition that actin—NPF binding to site-1 promotes. By binding to Arp3, Arpin directly competes with actin—NPF binding to site-2.
