title: The structure of kinetoplast DNA. 2. Characterization of a novel component of high complexity present in the kinetoplast DNA network of Crithidia luciliae.
abstract: 1. Degradation of highly purified kinetoplast DNA (kDNA) networks with restriction endonucleases yields "extra" bands in agarose gels that are absent from digests of mini-circles. Each of the five endonucleases tested, i.e. AluI, HapII, EcoRI, Hsu and HindII + III, yields a unique set of "extra" bands. The "extra" bands consist of linear DNA; they are not mini-circle oligomers and their added molecular weight, calculated from mobility in gels, are around 2 X 10(7). Double digests with two restriction endonucleases yield a new set of "extra" bands, showing that the "extra" bands obtained with different enzymes are all derived from the same complex component of kDNA. In digests of 32P-labelled kDNA an average of 2.3% of the radioactivity is recovered in the "extra" bands. 2. Treatment of kDNA networks with the single-strand-specific S1 nuclease of Aspergillus oryzae preferentially releases a linear DNA with a molecular weight of 26 X 10(6), calculated from mobility in gels. We present evidence that the 'extra' bands obtained with restriction endonucleases are derived from this component. 3. DNA-DNA renaturation analysis of fragmented kDNA shows the presence of a minor complex component with a complexity of about 3 X 10(7), making up less than 10% of the total kDNA. 4. From these results we conclude that 3--5% of the kDNA consists of a homogeneous class of maxi-circles catenated in the mini-circle network. The molecular weight of these maxi-circles is about 26 X 10(6) and they contain a unique, non-repetitive, non-mini-circle nucleotide sequence. This component is a prime candidate for the true mitochondrial DNA of trypanosomes.
mesh_terms: D000818:Animals; D004247:DNA; D004262:DNA Restriction Enzymes; D004270:DNA, Circular; D003851:Deoxyribonucleases; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D008854:Microscopy, Electron; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D009695:Nucleic Acid Renaturation; D014345:Trypanosoma / Q000032:analysis*
chemical_list: D004270:DNA, Circular; D004247:DNA; D003851:Deoxyribonucleases; D004262:DNA Restriction Enzymes