A Study on the Physico-chemical Properties of α-Actinin*

Abstract

1. Crude preparations of α-actinin were purified and separated into three components by ultracentrifugation. Some physico-chemical properties of each component were studied by sedimentation, viscosity and light scattering techniques. 2.S⁰₂₀, w of separated α-actinin component were found to be 6.2, 10.0 and 25.6. Each component had a remarkable accelerating effect on the superprecipitation of actomyosin and were similarly effective at equivalent concentration. 3. The 6S and 25S components were shown to have globular forms and possessed a low intrinsic viscosity in low ionic strength solutions. A pronounced characteristic of α-actinin was a lack of concentration dependence in several physico-chemical measurements which were carried out. 4. The molecular weights of the 6S and 25S component were determined by light scattering and sedimentation equilibrium techniques. The sizes of both components were discussed using the determined value of the molecular weight. 5. Each component was found to be depolymerized into its subunit, of which S₂₀, w was approximately 4S, in high concentration of urea. The structure and biological activity of each component was reversibly restored by eliminating urea from the solutions, except in the case of the 25S component which was converted to a mixture of 6S and 10S components.