Mitonafide (4-nitro-benzoisoquinolinedione) and a number of structural analogs were synthesized and studied in order to determine the structural requirements for inhibition of leishmanial nuclear and kinetoplast topoisomerase II and human topoisomerase II. The structure-activity relationship studies with the mitonafide analogs demonstrated that there was selective targeting of leishmanial nucle...

Instability is an intriguing characteristic of many protist genomes, and trypanosomatids are not exception in this respect. Some regions trypanosomatid genomes evolve fast. For instance, the mitochondrial (kinetoplast) genome consists fairly conserved maxicircle minicircle molecules that can, nevertheless, possess high nucleotide substitution rates between closely related strains. Recent experi...

Trypanosomes have an unusual mitochondrial genome, called kinetoplast DNA, that is a giant network containing thousands of interlocked minicircles. During kinetoplast DNA synthesis, minicircles are released from the network for replication as theta-structures, and then the free minicircle progeny reattach to the network. We report that a mitochondrial protein, which we term p38, functions in ki...

The electron microscopical aspect of kinetoplast DNA has been studied in preparations obtained by osmotic disruption of isolated organelles. A large amount of this DNA appears to be of large molecular size. This is apparently at variance with the observations, made by others using a different technical approach, of kinetoplast DNA consisting mainly of small circular molecules of constant size. ...

Kinetoplast DNA, the mitochondrial DNA of trypanosomatid parasites, is a network containing several thousand minicircles and a few dozen maxicircles. We compared kinetoplast DNA replication in Trypanosoma brucei and Crithidia fasciculata using fluorescence in situ hybridization and electron microscopy of isolated networks. One difference is in the location of maxicircles in situ. In C. fascicul...

We discuss here some results which suggest that radically different maxicircle classes coexist within the same kinetoplast. These data, although tentative and incomplete, may provide a new outlook on the kinetoplast genome structure and expression.

Members of the protozoan order Kinetoplastida (Honigberg et al., 1964), which includes the genera Trypanosoma, Leishmania, and Crithidia, are characterized by the presence of a body known as a kinetoplast. The kinetoplast is a modified region of a mitochondrion (Meyer et al., 1958; Steinert, 1960; Clark and Wallace, 1960) which contains so much DNA that it can be detected by Feulgen staining (B...

In trypanosomes, the large mitochondrial genome within the kinetoplast is physically connected to the flagellar basal bodies and is segregated by them during cell growth. The structural linkage enabling these phenomena is unknown. We have developed novel extraction/fixation protocols to characterize the links involved in kinetoplast-flagellum attachment and segregation. We show that three speci...

The structure of a C11 peptidase PmC11 from the gut bacterium, Parabacteroides merdae, has recently been determined, enabling the identification and characterization of a C11 orthologue, PNT1, in the parasitic protozoon Trypanosoma brucei. A phylogenetic analysis identified PmC11 orthologues in bacteria, archaea, Chromerids, Coccidia, and Kinetoplastida, the latter being the most divergent. A p...

It is well known that several antitrypanosomatid drugs accumulate in the parasite's mitochondrion, where they often bind to the organellar DNA, the kinetoplast. To what extent this property relates to the mode of action of these compounds has remained largely unquantified. Here we show that single point mutations that remove the dependence of laboratory strains of the sleeping sickness parasite...