The isolation of deoxyribonucleic acid from lamb heart mitochondria.

Recently, our laboratory reported the detection of small amounts of DNA in lamb heart mitochondria (1, 2). Experimental evidence indicated that this DNA was not merely a contaminant, but fulfilled a biologically active role in mitochondrial protein synthesis (2, 3). This was established by the observation that a DNA-dependent RNA polymerase was present in the mitochondria (2, 4, 5). These observations substantiate electron microscopic data which indicated the presence of mitochondrial fibers with DNA characteristics in representative cell types from plants and various animal phyla ranging from protozoa to higher vertebrates (6-8). A number of autoradiographic studies have also supported the mitochondrial localization of DNA (9-11). While our studies were in progress, two reports appeared, one by Luck and Reich (5) describing the isolation and purification of a DNA of unique buoyant density from Neurospora mitochondria, and another by Rabinowitz et al. (12), which presented evidence that mitochondria of avian heart and liver contain DNA which differs in its buoyant density from nuclear DNA. The experiments to be reported here describe a procedure for the isolation of DNA from purified lamb heart mitochondria and establish that this DNA also has a unique buoyant density.