Study of the ability of mitochondrial proteins to interact with actin

Using affinity chromatography of F-actin-sepharose 4B, the ability of proteins from rat liver submitochondrial fractions to interact with rabbit skeletal muscle actin was studied. The bulk of the actin-bound components was detected in the soluble compartments of the mitochondria, i.e., mitochondrial matrix and intermembrane space. The interaction was predominantly weak, since the desorption of the proteins from the column occurred at increased ionic strength of the solution. In membrane fractions, four polypeptides with Mr 65 000, 62 000, 59 000 and 10 500 eluting from the column only under effects of denaturating agents were predominant, thus suggesting the specificity of their binding to the immobilized actin. In a model system involving mitochondrial enzyme preparations (cytochrome c, glutamate dehydrogenase, isocitrate dehydrogenase, catalase), the possibility of their adsorption of F-actin-sepharose was investigated. It was shown that the highest adsorption capacity was observed in the case of immobilized actin with respect to catalase, the lowest one-to glutamate dehydrogenase. The data obtained suggest that the interaction of the actin-like mitochondrial protein with the system of solubilized enzymes may serve as a basis for their normal functioning.