Nucleic Acids Research, 2003, Vol. 31, No. 18 5305-5316
© 2003 Oxford University Press
Functional dissection of the C-terminal domain of type II DNA topoisomerase from the kinetoplastid hemoflagellate Leishmania donovani
Department of Molecular Parasitology, 1 Department of Drug Design, Development and Molecular Modeling, Indian Institute of Chemical Biology, Kolkata 700032, India and 2 Sealy Center for Molecular Sciences, University of Texas Medical Branch at Galveston, Galveston, TX 77555, USA
*To whom correspondence should be addressed. Tel: +91 33 2412 3207; Fax: +91 33 2473 5197; Email: hkmajumder{at}iicb.res.in
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors
The amino acid sequences of the C-terminal domain (CTD) of the type II DNA topoisomerases are divergent and species specific as compared with the highly conserved N-terminal and central domains. A set of C-terminal deletion mutants of Leishmania donovani topoisomerase II was constructed. Removal of more than 178 amino acids out of 1236 amino acid residues from the C-terminus inactivates the enzyme, whereas removal of 118 amino acids or less has no apparent effect on the ability of the parasite enzyme to complement a temperature-sensitive mutation of the Saccharomyces cerevisiae topoisomerase II gene. Deletion analysis revealed a potent nuclear localization signal (NLS) within the amino acid residues 998–1058. Immunomicroscopy results suggest that the removal of an NLS in the CTD is likely to contribute to the physiological dysfunction of these proteins. Modeling of the LdTOP2 based on the crystal structure of the yeast type II DNA topoisomerase showed that the parasite protein assumes a structure similar to its yeast counterpart harboring all the conserved residues in a structurally similar position. However, a marked difference in electrostatic potential was found in a span of 60 amino acid residues (998–1058), which also do not have any homology with topoisomerase II sequences. Such significant differences can be exploited by the structure-based design of selective inhibitors using the structure of the Leishmania enzyme as a template.
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