Nucleic Acids Research Advance Access originally published online on July 4, 2008
Nucleic Acids Research 2008 36(13):4465-4473; doi:10.1093/nar/gkn410
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Nucleic Acids Research, 2008, Vol. 36, No. 13 4465-4473
© 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.
Nucleic Acid Enzymes |
TbMP42 is a structure-sensitive ribonuclease that likely follows a metal ion catalysis mechanism
1Genetics, Darmstadt University of Technology, Schnittspahnstraße 10, 64287 Darmstadt and 2Computational Biology, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
*To whom correspondence should be addressed. Tel: +49 6151 16 28 55; Fax: +49 6151-16 56 40; Email: goringer{at}hrzpub.tu-darmstadt.de
Received May 6, 2008. Revised June 10, 2008. Accepted June 10, 2008.
RNA editing in African trypanosomes is characterized by a uridylate-specific insertion and/or deletion reaction that generates functional mitochondrial transcripts. The process is catalyzed by a multi-enzyme complex, the editosome, which consists of approximately 20 proteins. While for some of the polypeptides a contribution to the editing reaction can be deduced from their domain structure, the involvement of other proteins remains elusive. TbMP42, is a component of the editosome that is characterized by two C2H2-type zinc-finger domains and a putative oligosaccharide/oligonucleotide-binding fold. Recombinant TbMP42 has been shown to possess endo/exoribonuclease activity in vitro; however, the protein lacks canonical nuclease motifs. Using a set of synthetic gRNA/pre-mRNA substrate RNAs, we demonstrate that TbMP42 acts as a topology-dependent ribonuclease that is sensitive to base stacking. We further show that the chelation of Zn2+ cations is inhibitory to the enzyme activity and that the chemical modification of amino acids known to coordinate Zn2+ inactivates rTbMP42. Together, the data are suggestive of a Zn2+-dependent metal ion catalysis mechanism for the ribonucleolytic activity of rTbMP42.
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