Jagadish Babu Dasari - Department of Biology, University of Rome Tor Vergata, Via Della Ricerca Scientifica ۱, ۰۰۱۳۳ Rome, Italy.
Bini Chhetri Soren - Department of Biology, University of Rome Tor Vergata, Via Della Ricerca Scientifica ۱, ۰۰۱۳۳ Rome, Italy.
Alessio Ottaviani - Department of Biology, University of Rome Tor Vergata, Via Della Ricerca Scientifica ۱, ۰۰۱۳۳ Rome, Italy.
Cinzia Tesauro - Department of Biology, University of Rome Tor Vergata, Via Della Ricerca Scientifica ۱, ۰۰۱۳۳ Rome, Italy & Present address: Department of Molecular Biology and Genetics, University of Aarhus, C.F MøllersAllè ۳, ۸۰۰۰ Aarhus C, Denmark.
Simona Marino - Department of Biology, University of Rome Tor Vergata, Via Della Ricerca Scientifica ۱, ۰۰۱۳۳ Rome, Italy.
Beatrice Messina - Department of Biology, University of Rome Tor Vergata, Via Della Ricerca Scientifica ۱, ۰۰۱۳۳ Rome, Italy.
Paola Fiorani - Department of Biology, University of Rome Tor Vergata, Via Della Ricerca Scientifica ۱, ۰۰۱۳۳ Rome, Italy & Institute of Translational Pharmacology, National Research Council, CNR, Via Del Fosso del Cavaliere ۱۰۰, Rome ۰۰۱۳۳, Italy.

Background: DNA topoisomerases 1B are a class of ubiquitous enzyme that solves the topological problems associated with biological processes such as replication, transcription and recombination. Numerous sequence alignment of topoisomerase 1B from different species shows that the lengths of different domains as well as their amino acids sequences are quite different. In the present study a hybrid enzyme, generated by swapping the N-terminal of Plasmodium falciparum into the corresponding domain of the human, has been characterized. Methods: The chimeric enzyme was generated using different sets of PCR. The in vitro characterization was carried out using different DNA substrate including radio-labelled oligonucleotides. Results: The chimeric enzyme displayed slower relaxation activity, cleavage and re-ligation kinetics strongly perturbed when compared to the human enzyme. Conclusions: These results indicate that the N-terminal domain has a crucial role in modulating topoisomerase activity in different species.  

N-terminal domain, Plasmodium falciparum topoisomerase 1B, Topoisomerase 1B.