Topoisomerase II of filarial parasite Setaria cervi: purification and characterization

DNA topoisomerases are ubiquitous enzymes which are involved in replication, transcription, recombination and repair of nucleic acids. DNA topoisomerase II of filarial parasite Setaria cervi was purified to homogeneity by use of cation exchange and affinity chromatography. The purified enzyme migrated on SDS-PAGE as a single band with molecular weight of ∼80 kDa and native molecular weight of the enzyme was found to be 175 kDa indicating the dimeric nature of the protein. Topo II of S. cervi required ATP and dATP for its activity and optimal activity was observed at 1.0 mM ATP concentration. The filarial enzyme also utilized nucleotides, namely GTP, UTP and CTP for its activity. The divalent metal ions requirement of the enzyme showed that beside Mg+2 other ions viz., Ca+2, Mn+2, Cu+2 and Sr+2 were also utilized as cofactor for the activity. Antifilarial compounds ivermectin and diethylcarbamazine inhibited 100 % topo II activity at 100 μM concentration but suramin showed similar effect at 20 μM concentration. Nalidixic acid and novobiocin exhibited 100 % inhibition of the enzyme activity while mAMSA and etoposide inhibited the activity to different extents at 100 μM concentration. In view of significant differences in properties exhibited by the filarial topoisomerase as compared to other parasitic and eukaryotic topoisomerases, the filarial topoisomerase can be usefully exploited to devise new antifilarial compounds.