Studies on Gel Fraction in Fish Muscle Protein Extracts-VII

Actin Component in the Gell Fraction

Abstract

It has been reported that a myosin-like protein component was found in the dissociation products of the gel fraction treated with ATP or pyrophosphate. In order to determine whether the gel fraction contains actin, some properties of the aqueous extracts of the acetone-treated gel fraction were examined.
The gel fraction and actomyosin prepared from frozen or ice-stored muscles of the flatfish, Kareius bicoloratus were treated with acetone and extracted with cold water respectively. When 0.1M KCl and 1mM MgCl₂ were added to the aqueous extracts of the acetone-treated gel fraction, an increase in viscosity and a development of flow birefringence were observed. Furthermore, superprecipitation occurred when ATP was added to the combined system of myosin and the aqueous extracts of the acetone-treated gel fraction. The actin solution prepared from fresh muscle and the aqueous extracts from the acetone-treated actomyosin had similar viscosity, flow birefringence and superprecipitation properties. These results indicate that the gel fraction contains actin. From the results obtained in the series of the studies, it may be concluded that the gel fraction is an aggregated actomyosin, in which actin and myosin-like components are hypothesized to exist in a similar bound state.