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Mitochondrial DNA of the human malarial parasite Plasmodium falciparum
M J Gardner1, P A Bates, I T Ling
1Division of Parasitology, National Institute for Medical Research, London, U.K.
Abstract:
Covalently closed circular DNA molecules were isolated from Plasmodium falciparum total DNA by isopycnic centrifugation in CsCl gradients containing either ethidium bromide or 2',6-diamidino-2-phenylindole. The circular molecules had an average contour length of 11.1 +/- 0.5 micron, similar to the analogous molecules previously isolated from the simian malaria parasite P. knowlesi. Both circular molecules shared considerable sequence homology and conserved restriction sites. The nucleotide sequence of one 936 bp fragment of the P. falciparum molecule was determined and identified, by a data base homology search, as part of a mitochondrial small rRNA subunit, thus confirming the mitochondrial origin of the circular DNAs of both malarial species.
Insights
Researchers isolated circular DNA from Plasmodium falciparum, finding it shares similarities with Plasmodium knowlesi DNA. This confirms the mitochondrial origin of these circular DNA molecules in both malaria parasites.
Area of Science:
- Molecular Biology
- Parasitology
- Genetics
Background:
- Covalently closed circular DNA (cccDNA) plays crucial roles in various organisms.
- Understanding the nature and origin of cccDNA in malaria parasites is vital for parasitic disease research.
Purpose of the Study:
- To isolate and characterize covalently closed circular DNA molecules from Plasmodium falciparum.
- To investigate the sequence homology and origin of these circular DNA molecules by comparing them with those from Plasmodium knowlesi.
Main Methods:
- Isopycnic centrifugation in cesium chloride (CsCl) gradients with intercalating agents (ethidium bromide or 2',6-diamidino-2-phenylindole).
- Determination of average contour length of isolated circular DNA molecules.
- Nucleotide sequencing of a DNA fragment and database homology search.
Main Results:
- Circular DNA molecules were successfully isolated from Plasmodium falciparum.
- The isolated molecules exhibited an average contour length of 11.1 +/- 0.5 micron, comparable to Plasmodium knowlesi.
- Significant sequence homology and conserved restriction sites were observed between P. falciparum and P. knowlesi circular DNAs.
- A sequenced fragment of P. falciparum circular DNA was identified as part of a mitochondrial small ribosomal RNA (rRNA) subunit.
Conclusions:
- The study confirms the mitochondrial origin of covalently closed circular DNA in both Plasmodium falciparum and Plasmodium knowlesi.
- Shared characteristics suggest a conserved function or evolutionary history of mitochondrial circular DNA in these malaria parasites.