Mitochondrial DNA polymerase from Xenopus laevis oocytes (original) (raw)
1979, Biochemical and Biophysical Research Communications
The DNA polymerase of Xenopus laevis oocytes, with characteristics similar to those of the y polymerases of other systems, can be extracted from the mitochondrial pellet and from the mitochondria purified on a sucrose gradient. It elutes from phosphocellulose at about 0.4 M KCI and sediments faster than 4 S in high salt glycerol gradients. At low KCI concentrations it uses Poly(A) better than activated DNA as a template; the reverse is true at KCI concentrations higher than 150 mM. Various experiments are presented that indicate that it is the mitochondrial DNA pol~n~erase. In a previous report we have described the major DNA polymerase activity able to use Poly(A)-oligo(dT) as a template in Xengpus laevis oocytes (l). This enzyme has characteristics similar to those of the ~ pol3anerases of other systems, in that it efficiently uses Poly(A).oligo(dT) as a template, has a sedimentation coefficient higher than 4S and is sensitive to N'ethylmaleimide (2). The enzyme has a strict cytoplasmic location in these cells and is present in a particulate structure so that detergent is needed for its solubilization (I, 3). When detergent was omitted during the homogenization of the oocytes, virtually all the enzyme could be extracted from a 12,000 xg pellet; since mitochondria are the major component of this pellet, we decided to investigate the possibility that the enzyme is the mitochondrial DNA polymerase. In this paper we present experiments that support this hypothesis. MATERIALS AND METHODS Materials. Deoxynucleotide-5'-triphosphates were obtained from Schwartz Mann, Orangeburg, N.Y.
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