PANKINETOPLAST DNA-STRUCTURE IN A PRIMITIVE BODONID FLAGELLATE, CRYPTOBIA-HELICIS

The mitochondrial DNA (mtDNA) of a primitive kinetoplastid flagellate Cryptobia helicis is composed of 4.2 kb minicircles and 43 kb maxicirc les. 85% and 6% of the minicircles are in the form of supercoiled (SC) and relaxed (OC) monomers, respectively, The remaining minicircles (9 %) constitute catenated oligomers composed of both the SC and OC molec ules. Minicircles contain bent helix and sequences homologous to the m inicircle conserved sequence blocks, Maxicircles encode typical mitoch ondrial genes and are not catenated. The mtDNA, which we describe with the term 'pankinetoplast DNA', is spread throughout the mitochondrial lumen, where it is associated with multiple electron-lucent loci. The re are similar to 8400 minicircles per pankinetoplast-mitochondrion, w ith the pan-kDNA representing similar to 36% of the total cellular DNA , Based on the similarity of the C. helicis minicircles to plasmids, w e present a theory on the formation of the kDNA network.