THE GENE ENCODING TOPOISOMERASE-II FROM PLASMODIUM-FALCIPARUM

The gene for topoisomerase II has been isolated from genomic libraries of strain K1 of the human malarial parasite, Plasmodium falciparum. T he sequence reveals an open reading frame of 4194 nucleotides which pr edicts a polypeptide of 1398 amino acids. There are apparently no intr ons. The sequence is present as a single copy which has an identity of 47.4% and a similarity of 65.4% with its human homologue. Sequences c onserved in topoisomerase II from other species are present in Pftopoi somerase II but in addition it has two adjacent asparagine-rich insert ions which are unique to it. We have also detected asparagine-rich reg ions in the gene for PfDNA polymerase alpha. The gene for Pftopoisomer ase II has been localised to chromosome 14 and northern analysis revea ls a transcript of 5.8kb. Two independent antisera raised;in mice agai nst glutathione-S-transferase fusion proteins containing the amino ter minal portion of the malarial protein detect a weak band on western bl ots at about 160kDa, the expected size of the protein. Use of the same antisera for immunofluorescence analysis suggests that the protein is present at all stages of intraerythrocytic growth of the parasite.