Single-molecule visualization of a formin-capping protein ‘decision complex’ at the actin filament barbed end

摘要: Precise control of actin filament length is essential to many cellular processes. Formins processively elongate filaments, whereas capping protein (CP) binds barbed ends and arrests polymerization. While genetic biochemical evidence has indicated that these two proteins function antagonistically, the mechanism underlying antagonism remained unresolved. Here we use multi-wavelength single-molecule fluorescence microscopy observe fully reversible formation a long-lived 'decision complex' in which CP dimer formin mDia1 simultaneously bind end. Further, displaced from end by can randomly slide along later return re-form complex. Quantitative kinetic analysis reveals CP-mDia1 vitro occurs through decision Our observations suggest new molecular mechanisms for capture cells.