Expression of the mitochondrial genome in HeLa cells. XVI. Electrophoretic properties of the products of in vivo and in vitro mitochondrial protein synthesis

The size distribution of the proteins synthesized by isolated HeLa cell mitochondria has been analyzed by polyacrylamide gel electrophoresis and compared to that of the in vivo products of mitochondrial protein synthesis.The electrophoretic pattern of the mitochondrial proteins labeled in vitro with [³H]leucine has a group of partially resolved components migrating in the region corresponding to 12,000 to 25,000 molecular weight, and another group, more abundant, in the range from 40,000 to 55,000 molecular weight. This pattern is very similar, after a two-hour incubation of mitochondria, to that of the proteins labeled in vivo in a 30-minute [³H]leucine pulse.