Which of the following proteins acts as a nucleation promoting factor for the Arp2/3 complex?
Arp2/3 mediated branch formation depends on nucleation promoting factors bearing C central A acidic region plus WH2 actin binding motifs. Endogenous factors include N WASP activated by Cdc42 and PIP2 in endocytosis and filopodia, WAVE activated by Rac at lamellipodia, WHAMM at Golgi. Bacterial pathogens mimic motif to hijack host cytoskeleton. ActA surface protein of Listeria monocytogenes 639 amino acids contains N terminal polycationic stretch, central proline rich repeats binding Ena VASP and acidic actin binding motifs functioning as VCA equivalent recruiting Arp2/3 with affinity 0.3 micro
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 16: ActA as NPF for Arp2/3 Activation.