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Archaea
Volume 2016 (2016), Article ID 7316725, 14 pages
http://dx.doi.org/10.1155/2016/7316725
Research Article

Deciphering the Translation Initiation Factor 5A Modification Pathway in Halophilic Archaea

1Department of Microbiology and Cell Science, Institute for Food and Agricultural Sciences and Genetic Institute, University of Florida, P.O. Box 110700, Gainesville, FL 32611-0700, USA
2Gene Center and Department for Biochemistry, University of Munich, 81377 Munich, Germany
3Center for Integrated Protein Science Munich, University of Munich, 81377 Munich, Germany
4Faculty of Science and Technology, Institute of Technology, University of Tartu, Tartu, Estonia
5Department of Molecular and Cell Biology, University of Connecticut, 91 N. Eagleville Rd, Storrs, CT 06269, USA
6Institute of Environmental Microbiology, Kyowa Kako Co. Ltd., Tadao 2-15-5, Machida 194-0035, Japan

Received 7 September 2016; Revised 27 October 2016; Accepted 6 November 2016

Academic Editor: Michael Ibba

Copyright © 2016 Laurence Prunetti 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.

Abstract

Translation initiation factor 5A (IF5A) is essential and highly conserved in Eukarya (eIF5A) and Archaea (aIF5A). The activity of IF5A requires hypusine, a posttranslational modification synthesized in Eukarya from the polyamine precursor spermidine. Intracellular polyamine analyses revealed that agmatine and cadaverine were the main polyamines produced in Haloferax volcanii in minimal medium, raising the question of how hypusine is synthesized in this halophilic Archaea. Metabolic reconstruction led to a tentative picture of polyamine metabolism and aIF5A modification in Hfx. volcanii that was experimentally tested. Analysis of aIF5A from Hfx. volcanii by LC-MS/MS revealed it was exclusively deoxyhypusinylated. Genetic studies confirmed the role of the predicted arginine decarboxylase gene (HVO_1958) in agmatine synthesis. The agmatinase-like gene (HVO_2299) was found to be essential, consistent with a role in aIF5A modification predicted by physical clustering evidence. Recombinant deoxyhypusine synthase (DHS) from S. cerevisiae was shown to transfer 4-aminobutyl moiety from spermidine to aIF5A from Hfx. volcanii in vitro. However, at least under conditions tested, this transfer was not observed with the Hfx. volcanii DHS. Furthermore, the growth of Hfx. volcanii was not inhibited by the classical DHS inhibitor GC7. We propose a model of deoxyhypusine synthesis in Hfx. volcanii that differs from the canonical eukaryotic pathway, paving the way for further studies.