Effect of β-actinin on the particle length of F-actin

The binding of β-actinin, the actin-dispersing factor, to F-actin has been investigated. The stoichiometric ratios for the binding of β-actinin to F-actin were found to be 1:10 and 1:8, by weight, for intact and sonicated F-actin, respectively.

When an increasing amount of β-actinin was added to F-actin and subjected to sonication, F-actin could be dispersed into particles as short as 3000–4000 Å. Such short F-actin particles were also formed when G-actin was polymerized in the presence of a large amount of β-actinin.

Experimental conditions were checked for the action of β-actinin on the apparent particle length of F-actin. β-Actinin was found to become slowly inactivated in 0.1 M KCl.