The effect of intact talin and talin tail fragment on actin filament dynamics and structure depends on pH and ionic strength

We employed quasi-elastic light scattering and electron microscopy to inves tigate the influence of intact talin and talin tail fragment on actin filam ent dynamics and network structure. Using these methods, we confirm previou s reports that intact talin induces cross-linking as well as filament short ening on actin networks. We now show that the effect of intact talin as wel l as talin tail fragment on actin networks is controlled by pH and ionic st rength. At pH 7.5, actin filament dynamics in the presence of intact talin and talin tail fragment are characterized by a rapid decay of the dynamic s tructure factor and by a square root power law for the stretched exponentia l decay which is in contrast with the theory for pure actin solutions. At p H 6 and low ionic strength, intact talin cross-links actin filaments more t ightly than talin tail fragment. Talin head fragment showed no effect on ac tin networks, indicating that the actin binding sites reside probably exclu sively within the tail domain.