PROPERTIES OF MITOCHONDRIAL-DNA POLYMERASE IN MITOCHONDRIAL-DNA SYNTHESIS IN YEAST

Mitochondrial DNA polymerase from Saccharomyces cerevisiae, purified 3 500 fold, was separated by sodium dodecyl sulfate-polyacrylamide gel e lectrophoresis into three polypeptides. The major 150 kDa polypeptide was probably the catalytic subunit of the mitochondrial (mt) DNA polym erase and the other two polypeptides could be either proteolytic cleav age products of the polymerase, other subunits of the enzyme or protei n contaminants. The mtDNA polymerase preferred an A+T-rich DNA templat e and did not require any RNA primer for DNA synthesis, at least under in vitro reaction conditions. It showed higher processivity on a doub le-stranded linear DNA template than on a single-stranded circular DNA template, and was capable of synthesizing at least about 1200 nucleot ide primer-extended products without any major pause on a double-stran ded DNA template.