[Interpretation of the low rate of polypeptide synthesis in mitochondria in vitro]

The distribution of radioactivity between the growing and finally formed polypeptides in rat liver mitochondria incubated with labelled amino acids was studied. The rate of an "average" polypeptide synthesis in the mitochondrial translation system is much lower than that in bacterial and eukaryotic cytoplasmic protein synthesizing systems. A kinetic study of mitochondrial polypeptide labelling suggests that the rate of ribosomal movement along mRNA in mitochondrial translation systems is variable. It is assumed that the low rate of polypeptide synthesis in mitochondria is due to the delay in ribosome movement along the middle part of mRNA.