Assembly of the Mitochondrial Membrane System: VIII. PROPERTIES OF THE PRODUCTS OF MITOCHONDRIAL PROTEIN SYNTHESIS IN YEAST

Abstract

Abstract The products of mitochondrial protein synthesis in yeast have been studied by analytical gel electrophoresis. Over 60% of the total counts incorporated into mitochondria when cytoplasmic protein synthesis is blocked are associated with five proteins which are separated on acrylamide gels in the presence of sodium dodecyl sulfate. The mitochondrial products have been found to be extracted from the membrane with acidic chloroform-methanol. Under neutral conditions chloroform-methanol removes predominantly a protein which has been estimated to have a molecular weight of 7,800. This protein has been found to be present in the membrane in a polymeric form with an apparent molecular weight of 45,000. Conversion of the polymer to the low molecular weight form is achieved by treatment of mitochondrial membranes with chloroform-methanol or by depolymerization in sodium dodecyl sulfate at alkaline pH. The low molecular weight protein appears to be the major product of mitochondrial protein synthesis. Its possible role in mitochondrial biogenesis is discussed.