Sequence organization of rat brain mitochondrial DNA.

The sequence organization of rat brain and liver mitochondrial (mt) DNA has been characterized using restriction endonucleases HindIII, BamHI, HhaI, and HaeIII. There is no evidence of heterogeneity on the base sequence of liver or brain mt DNA. The liver and brain mtDNAs were found to produce identical DNA fragments using these enzymes. Both the liver and brain mtDNA were analyzed by enzymatic digestions using HpaII/MspI. There was no evidence of the presence of methylated cytosine residues. Six different recombinant DNA molecules were analyzed by HindIII restriction digests and found to contain all of the 6 mtDNA fragments. Recombinant DNA molecules were analyzed for their molecular sizes by electron microscopy. The recombinant DNAs again showed the mtDNA fragments to have the right molecular weight. The molecular sizes of the recombinant DNA molecules were found to be 10.4, 7.4, 6.1, 5.7, 4.7 and 4.1 kilobase pairs (kbp). These molecular sizes reflect the insertion of 6.1, 3.8, 2.3, 1.9, 0.8 and 0.1 kbp HindIII mtDNA fragments in pBR322. The presence of mtDNA fragments in recombinant DNA molecules was also confirmed by hybridizing the nick translated brain mtDNA with Southern transfers of the recombinant DNA molecules.