Expression and characterization of the ATP-binding domain of a malarial Plasmodium vivax gene homologous to the B-subunit of the bacterial topoisomerase DNA gyrase.

We have previously reported the presence of a DNA gyrase-like topoisomerase activity associated with the 35kb apicoplast DNA in the malarial parasite Plasmodium falciparum [Weissig V, Vetro-Widenhouse TS, Rowe TC. Topoisomerase II inhibitors induce cleavage of nuclear and 35kb plastid DNAs in the malarial parasite Plasmodium falciparum. DNA Cell Biol 1997;16:1483]. Sequences encoding polypeptides homologous to both the A and B subunits of bacterial DNA gyrase have been identified in the genome sequence of P. falciparum among data produced by the Malaria Genome Consortium and the University of Florida Malaria Gene Sequence Tag Project. Based on these findings, we have cloned and expressed a region of the Plasmodium vivax GyrB gene encoding a 43kDa polypeptide homologous to the ATP-binding domain of Escherichia coli DNA gyrase. The 43kDa PvGyrB polypeptide was found to have intrinsic ATPase activity with a K(m) of 0.27mM and a k(cat) of 0.051s(-1). The PvGyrB ATPase was also sensitive to the bacterial DNA gyrase inhibitor coumermycin. The implications of these findings are discussed.