Protomitohondria from liver cells: Similarities with and differences from mitochondria

Abstract

In this study, we continue the investigation of a number of the properties of protomitochondria, which are young mitochondria of a smaller size that are present in animal cells. The protomitochondria were obtained from the rat liver by filtration of a total mitochondrial suspension through Millipore filters. The organelles contain the active respiratory chain as shown by the high rate of oxygen consumption during succinate and NADH oxidation. The shunt activity of succinate-tetrazolium reductase was lower and the activity of NADH-tetrazolium reductase was higher as compared with those in mitochondria. According to gel electrophoresis and gel filtration no qualitative differences between protomitochondria (0.25–0.45 µm) and mitochondria in their major protein composition were found. Nevertheless, there were some quantitative differences in several bands. Perhaps these differences reflect the process of intracellular maturation of protomitochondria to mitochondria. The data we obtained are important for understanding mitochondriogenesis in the animal cell.