Thymus actin: preparation and characterization

A combination of the C-gamma alumina adsorption technique of Lindberg, U. Skoog, L. 1970. Eur. J. Biochem. 13 326-335 with the traditional actin purification procedure (polymerization-depolymerization) yielded a simple method for the preparation of actin from fresh or acetone-dried thymus tissue. Actin obtained by this procedure from thymus was homogeneous and comigrated with skeletal actin in SDS gel electrophoresis. In isoelectric focusing it was shown to contain beta and gamma actin. Thymus actin polymerized poorly or not at all. It was native, however, as judged from its DN-ase I inhibiting activity which equalled that of skeletal actin. It also activated skeletal myosin ATP-ase but to a lesser extent than skeletal actin. On addition of HMM to thymus G actin, decorated filaments formed abundantly.