title: Allosteric activation of trypanosomatid deoxyhypusine synthase by a catalytically dead paralog.
abstract: Polyamine 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.
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041, USA.
authors.forename: Suong
authors.initials: S
authors.lastname: Nguyen
authors.forename: Deuan C
authors.initials: DC
authors.lastname: Jones
authors.forename: Susan
authors.initials: S
authors.lastname: Wyllie
authors.forename: Alan H
authors.initials: AH
authors.lastname: Fairlamb
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Phillips
mesh_terms: D000818:Animals; D002417:Cattle; D004926:Escherichia coli; D055785:Gene Knockdown Techniques; D006801:Humans; D008239:Lysine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051379:Mice; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013095:Spermidine / Q000737:chemistry / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D014354:Trypanosomiasis, Bovine / Q000201:enzymology / Q000235:genetics
chemical_list: D015800:Protozoan Proteins; D011994:Recombinant Proteins; C100028:hypusine; D000587:Oxidoreductases Acting on CH-NH Group Donors; C063507:deoxyhypusine synthase; D008239:Lysine; D013095:Spermidine
keywords: Deoxyhypusine; Deoxyhypusine Synthase; Parasite Metabolism; Polyamines; Protozoan; Spermidine; Trypanosoma brucei; Trypanosome; eIF5A