On the Purification of Actin from Fish Muscle

Abstract

Actin was extracted from the acetone dried muscle powder of tilapia, Tilapia mossambica, and purified by reversible polymerization and gel filtration on Sephadex G-200 to electro-phoretic homogeneity as shown by SDS-polyacrylamide gels.
The purified G-actin retains the ability to polymerize into F-actin in the presence of 0.1_M KCI plus 1m_M MgCl_2. Its mobility on SDS-polyacrylamide gel electrophoresis is identical with that of carp and rabbit actin.
The purified actin complexed with tilapia myosin to form actomyosin desensitized to the action of Ca²⁺; in the absence of Ca²⁺, superprecipitation of the synthetic actomyosin was inhibited by the addition of a tropomyosin-troponin complex prepared from tilapia or carp muscle, the addition of Ca²⁺ releasing the inhibition. These observations clearly indicate that the actin, purified from tilapia muscle, is devoid of the tropomyosin-troponin complex.