6dft
From Proteopedia
Trypanosoma brucei deoxyhypusine synthase
Structural highlights
Function[DHYSC_TRYB2] In association with the non-catalytic regulatory subunit DHSp, catalyzes the NAD-dependent oxidative cleavage of spermidine and the subsequent transfer of the butylamine moiety of spermidine to the epsilon-amino group of a specific lysine residue of the eIF5A precursor protein to form the intermediate deoxyhypusine residue. Regulates protein levels of its regulatory subunit DHSp. Required for cell growth and survival.[1] [DHYSP_TRYB2] Required for the activation and stability of deoxyhypusine synthase DHSc. Required for cell growth and survival.[2] Publication Abstract from PubMedPolyamine biosynthesis is a key drug target in African trypanosomes. The "resurrection drug" eflornithine (difluoromethylornithine), which is used clinically to treat human African trypanosomiasis, inhibits the first step in polyamine (spermidine) biosynthesis, a highly regulated pathway in most eukaryotic cells. Previously, we showed that activity of a key trypanosomatid spermidine biosynthetic enzyme, S-adenosylmethionine decarboxylase, is regulated by heterodimer formation with a catalytically dead paralog (a prozyme). Here, we describe an expansion of this prozyme paradigm to the enzyme deoxyhypusine synthase, which is required for spermidine-dependent hypusine modification of a lysine residue in the essential translation factor eIF5A. Trypanosoma brucei encodes two deoxyhypusine synthase paralogs, one that is catalytically functional but grossly impaired, and the other is inactive. Co-expression in Escherichia coli results in heterotetramer formation with a 3000-fold increase in enzyme activity. This functional complex is also present in T. brucei, and conditional knock-out studies indicate that both DHS genes are essential for in vitro growth and infectivity in mice. The recurrent evolution of paralogous, catalytically dead enzyme-based activating mechanisms may be a consequence of the unusual gene expression in the parasites, which lack transcriptional regulation. Our results suggest that this mechanism may be more widely used by trypanosomatids to control enzyme activity and ultimately influence pathogenesis than currently appreciated. Allosteric activation of trypanosomatid deoxyhypusine synthase by a catalytically dead paralog.,Nguyen S, Jones DC, Wyllie S, Fairlamb AH, Phillips MA J Biol Chem. 2013 May 24;288(21):15256-67. doi: 10.1074/jbc.M113.461137. Epub, 2013 Mar 21. PMID:23525104[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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