Stabilizing Effect of Tropomyosin on Actin during Storage at Low Temperature

Abstract

The effects of tropomyosin (TM) on the stability of actin with and without heavy meromyosin (HMM) during storage at low temperature were studied by the DNase I inhibition assay. The stabilizing effect of TM on actin without ATP at 0°C was associated with the extent of binding of TM to the actin filaments that was dependent on the KCl concentrations: i.e., TM effectively depressed the denaturation of actin at a KCl concentration ranging from 0.1 to 0.5 M whereby TM can be bound to F-actin, Stabilization by TM could reduce the probability of the destabilization of actin due to a small amount of HMM. A combination of TM and a large amount of HMM strongly stabilized actin, even in a high salt concentration such as 0.6 M KCl These results indicate that tropomyosin played an important role in stabilizing actin in an actomyosin complex (natural actomyosin) during treatment with salt at a low temperature.