Denaturation of actomiosine from rabbit striated muscle by promethazine

Abstract

Interaction between Promethazine and contractile proteins prepared from rabbit striated muscle has been studied by methods based on the fact that the phenothiazinic compound acting upon actiomiosine causes a physical change in the protein, which results in the loss of the capability of changing from the F to the G forms. Measurements have been carried out on the effect of Promethazine to cause turbidity when added to a solution of actomiosine G. Furthermore, it has been shown that actiomiosine F is able to remove Promethazine from a solution to which both actomiosine F and Promethazine have been added in suitable preparations. When a solution of actiomiosine G is dropped over the surface of a column of distilled water, it changes to the F form showing a well round shapped and limited drop. However, when actomiosine G is previously treated with Promethazine in suitable concentrations, and it is dropped over the surface of a column of water, the drop of actomiosin F becomes shapeless by loosing its physical form. A method, called the “drop method” has been devised in order to quantitate this phenomenon due to the fact that such physical changes in the properties of actomiosine F are related to two parameters: the concentration of Promethazine and the height from which the dropping is carried out on the water surface.