Mitochondrial proteinase of yeast splitting the products of mitochondrial translation

: It has been shown that mitochondria of the yeast Saccharomyces cerevisiae contain proteinase, which is bound to the inner mitochondrial membrane and catalyzes the hydrolysis of mitochondrial translation products in vitro. The efficiency of proteolysis depends on the state of mitochondria: e.g. the degradation of completely formed organelles corresponding to stationary cells, is twice as low as compared to the "young" organelles typical for the beginning of a logarithmic phase of growth. The proteolysis of mitochondrial translation products can occur not only in mitochondria, but also in "inside out" submitochondrial particles. In order to prove the absence of concomitant vacuolar proteinases in preparations of mitochondria and submitochondrial particles, the specific antisera against proteinases A and B have been used. The activity of mitochondrial proteinase is completely inhibited by the natural peptide inhibitors antipain and chymostatin. Of special importance is the fact that another natural peptide inhibitor--leupeptin, having no effect on the activities of vacuolar proteinases, significantly decreases the rate of hydrolysis of mitochondrial translation products. The role of yeast mitochondrial proteinase in regulation of mitochondrial formation is discussed.