Identification of DNA-binding proteins in the parasitic protozoan Crithidia fasciculata and evidence for their association with the mitochondrial genome.

The single mitochondrion of trypanosomatid protozoans such as Crithidia fasciculata has a large and complex network of AT-rich DNA called kDNA. Little is known about proteins involved in the packaging and morphogenesis of this network. I report the purification of a protein fraction from this parasite which preferentially retained kDNA in the gel slot during electrophoresis. The proteins had approximate molecular weights of 22, 21, 17.5, 16.5, 15, and 13 kDa. They copurified with mitochondrial DNA, parts of which they protected from nuclease attack. The proteins resembled histones but they also differed from histones in significant ways. Immunological evidence showed that the proteins were enriched in a mitochondrial fraction, implying their association with kDNA in vivo.