Relationship between metabolic states of liver mitochondria and the G/F-actin ratio.

Liver mitochondria, incubated in a sucrose-buffered medium free of additives, contained more than half their total actin-like protein in the free or/unpolymerized form. Energization of mitochondria by means of substrate addition induced an orthodox configuration of these organelles and a significant increase in the content of globular actin. In contrast, the condensed state that arose following deenergization was associated with a significant increase in the content of the polymerized form of this protein. The occurrence of these two ultrastructural states was verified by electron microscopy. The variation observed in the content of the unpolymerized form of actin-like protein was confirmed in studies with phalloidin, which promotes actin polymerization. Thus, our results show that energy-linked ultrastructural transformations of mitochondria are to a certain degree correlated with the globular/fibrillar actin ratio.