What is the characteristic angle between the old and new filaments formed by the Arp2/3 complex?
Arp2/3 nucleation geometry defines dendritic array organization. Single particle cryo EM and platinum replica electron tomography of lamellipodia show mother filament and daughter filament meet at Y junction with outer angle about 70 degrees, interior acute angle 110 degrees due to filament twist. Daughter pointed end capped by Arp2/3 complex remaining at junction while barbed end grows outward facing membrane. Angle determined by binding mode: ARPC2 ARPC4 subunits clamp side of mother, Arp2 Arp3 arranged in short pitch to emulate filament barbed end, orienting daughter at defined angle constr
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 16: Arp2/3 Branch Angle 70 Degrees.
