[Kinetics of the biosynthesis and distribution of labelled actin-like proteins in rat liver submitochondrial fractions].

Affinity adsorption on immobilized DNAase I and the measurements of the protein mobility upon SDS-PAGE electrophoresis were used for the identification of the actin-like protein as well as for the study of its biosynthesis is liver mitochondria of hepatectomized rats. The kinetics of biosynthesis showed a maximum on the 10th min after intraperitoneal injection of the label. Fractionation of mitochondria demonstrated that more than 50% of the whole amount of the "de novo" synthesized protein is localized in the intermembrane space, approximately 30%--in the mitochondrial matrix. The purity of the fractions was controlled by analyzing the polypeptide content of the samples and by measuring the marker enzyme activity. Besides, additional identification of the actin-like protein was carried out directly in the mitochondrial matrix and intermembrane space by two-dimensional electrophoresis in polyacrylamide gel performed by the O'Farrell method. The subsequent staining of the gels with silver revealed the presence of two basic isoforms of non-muscle action (beta- and gamma-actins). The presence of the actin-like protein in the inner mitochondrial compartments characterized by a high rate of metabolism may be regarded as compelling evidence of its mitochondrial localization.