Absence of accessory subunit in the DNA polymerase gamma purified from yeast mitochondria.

In yeast and animals, replication of the mitochondrial genome is carried out by the DNA polymerase gamma. In mammals this polymerase is composed of a catalytic and an accessory subunit. Yeast DNA polymerase gamma was purified over 6600-fold from mitochondria. The catalytic polypeptide of this enzyme was identified as a 135-kDa protein by a photochemical crosslinking procedure and its native molecular weight was estimated between 120 and 140 kDa by gel filtration and glycerol gradient sedimentation. These results indicate that yeast DNA polymerase gamma contains only one subunit and thus has a different quaternary structure from its counterpart in animals.