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Journal of Biomedicine and Biotechnology
Volume 2009, Article ID 837608, 9 pages
Research Article

Functional Expression of a DNA-Topoisomerase IB from Cryptosporidium parvum

Departamento de Ciencias Biomédicas (INTOXCAL), Universidad de León, Campus de Vegazana s/n, 24071 León, Spain

Received 20 February 2009; Revised 20 May 2009; Accepted 28 May 2009

Academic Editor: Ali Ouaissi

Copyright © 2009 César Ordóñez et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Cryptosporidium parvum, one of the most important causative organisms of human diarrheas during childhood, contains a monomeric DNA-topoisomerase IB (CpTopIB) in chromosome 7. Heterologous expression of CpTopIB gene in a budding yeast strain lacking this activity proves that the cryptosporidial enzyme is functional in vivo. The enzymatic activity is comprised in a single polypeptide, which contains all the structural features defining a fully active TopIB. Relaxation activity of the yeast extracts was detected only when CpTopIB ORF was expressed in a yeast expression system showing time and protein dependence under steady state kinetic conditions. The susceptibility of CpTopIB-transformed yeast to the irreversible inhibitor camptothecin and its water-soluble derivatives (topotecan and SN-38) was assessed.