Sodium arsenite facilitates the turn-over of phosphate in cultured chicken myotube tropomyosin

Abstract

Both the α and β subunits of tropomyosin are phosphorylated in embryonic and adult skeletal muscle. Here we demonstrate that the phosphate groups on α- and β-tropomyosin in cultured chicken myogenic cells have half-lives of 7- and 21-hr, respectively under normal growth conditions. After sodium arsenite treatment, the half-lives of α- and β-tropomyosin phosphates are reduced to 1.5- and 5-hr, respectively. This facilitated phosphate turnover is reversible and may be specific for tropomyosin since it is not observed with other major phosphorylated proteins, such as the intermediate filament proteins desmin and vimentin. The results suggest that vicinal dithiols may be involved in the enzymatic activities which are responsible for the removal of phosphate from tropomyosin.