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The translation factor IF5A is highly conserved in Eukarya and Archaea and undergoes a unique post-translational hypusine modification by the deoxyhypusine synthase (DHS) enzyme. DHS transfers the butylamine moiety from spermidine to IF5A using NAD as a cofactor, forming a deoxyhypusine intermediate. IF5A is a key player in protein synthesis, preventing ribosome stalling in proline-rich sequences during translation elongation and facilitating translation elongation and termination. Additionally, human eIF5A participates in various essential cellular processes and contributes to cancer metastasis, with inhibiting hypusination showing anti-proliferative effects. The hypusination pathway of IF5A is therefore an attractive new therapeutic target. We elucidated the 2.0 Å X-ray crystal structure of the archaeal DHS-IF5A complex, revealing hetero-octameric architecture and providing a detailed view of the complex active site including the hypusination loop. This structure, along with biophysical data and molecular dynamics simulations, provides new insights into the catalytic mechanism of the hypusination reaction. [Display omitted] • Structural characterization of the archaeal aIF5A-aDHS complex • The complex presents a 4:4 (aIFA:aDHS) stoichiometry • The archaeal and human aIF5A-aDHS complexes are extremely conserved The research conducted by D'Agostino et al. unveils the high-resolution crystallographic structure of the archaeal protein complex IF5A-DHS revealing octameric architecture. The study offers a comprehensive insight into the enzyme's active site, responsible for initiating the hypusination reaction. [ABSTRACT FROM AUTHOR]

Summary Trypanosoma brucei is a neglected tropical disease endemic to Africa. The polyamine spermidine is essential for post-translational hypusine modification of eukaryotic initiation factor 5A (eIF5A), which is catalyzed by deoxyhypusine synthase (Tb DHS). In trypanosomatids, deoxyhypusine synthase (DHS) activity is dependent on heterotetramer formation between two paralogs, DHSc and DHSp, both with minimal activity on their own due to missing catalytic residues. We determined the X-ray structure of Tb DHS showing a single functional shared active site is formed at the DHSc/DHSp heterodimer interface, with deficiencies in one subunit complemented by the other. Each heterodimer contains two NAD+ binding sites, one housed in the functional catalytic site and the second bound in a remnant dead site that lacks key catalytic residues. Functional analysis of these sites by site-directed mutagenesis identified long-range contributions to the catalytic site from the dead site. Differences between trypanosomatid and human DHS that could be exploited for drug discovery were identified. Graphical Abstract Highlights • Crystal structure of Trypanosoma brucei deoxyhypusine synthase (DHS) is reported • Obligate heterotetrameric is formed between two paralogous pseudoenzymes • Enzyme activity is restored by active-site complementation • NAD+ binding sites show potential for selectivity compared with human DHS Afanador et al. determined the X-ray structure of an essential enzyme for survival of the eukaryotic pathogen Trypanosoma brucei. This enzyme is composed of two inactive paralogs, together forming an active heterotetramer via active-site complementation. This structure differs from the human homolog, highlighting the potential for species-selective inhibition. [ABSTRACT FROM AUTHOR]

Deoxyhypusine synthase (DHS) and deoxyhypusine hydroxylase (DOHH) are essential for hypusination of eukaryotic translation initiation factor 5A (eIF-5A). In this issue, Han et al. use X-ray crystallograpy and UV/Vis and Mössbauer spectroscopy to provide insights into the fundamental mechanism of the hypusination of eIF-5A and a peroxo intermediate state. [ABSTRACT FROM AUTHOR]