Nucleic Acids Research Advance Access originally published online on September 2, 2008
Nucleic Acids Research 2008 36(17):5645-5651; doi:10.1093/nar/gkn558
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Nucleic Acids Research, 2008, Vol. 36, No. 17 5645-5651
© 2008 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
Thr729 in human topoisomerase I modulates anti-cancer drug resistance by altering protein domain communications as suggested by molecular dynamics simulations
1CASPUR Inter-University Consortium for the Application of Super-Computing for Universities and Research, Via dei Tizii 6, Rome 00185, 2Department of Biology and Centro di Bioinformatica e Biostatistica, University of Rome Tor Vergata, Via Della Ricerca Scientifica, Rome 00133, 3Department of Biology, University of Padua, Via U. Bassi 58/B, Padua 35131 and 4National Institute for Infectious Diseases ‘L. Spallanzani’, Via Portuense 292, Rome 00149, Italy
*To whom correspondence should be addressed. Tel: +39 06 4486706; Fax: +39 06 4957083; Email: g.chillemi{at}caspur.it
Received June 10, 2008. Revised August 18, 2008. Accepted August 18, 2008.
The role of Thr729 in modulating the enzymatic function of human topoisomerase I has been characterized by molecular dynamics (MD) simulation. In detail, the structural–dynamical behaviour of the Thr729Lys and the Thr729Pro mutants have been characterized because of their in vivo and in vitro functional properties evidenced in the accompanying paper. Both mutants can bind to the DNA substrate and are enzymatically active, but while Thr729Lys is resistant even at high concentration of the camptothecin (CPT) anti-cancer drug, Thr729Pro shows only a mild reduction in drug sensitivity and in DNA binding. MD simulations show that the Thr729Lys mutation provokes a structural perturbation of the CPT-binding pocket. On the other hand, the Thr729Pro mutant maintains the wild-type structural scaffold, only increasing its rigidity. The simulations also show the complete abolishment, in the Thr729Lys mutant, of the protein communications between the C-terminal domain (where the active Tyr723 is located) and the linker domain, that plays an essential role in the control of the DNA rotation, thus explaining the distributive mode of action displayed by this mutant.