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Trypanosomatid Deoxyhypusine Synthase Activity Is Dependent on Shared Active-Site Complementation between

Gustavo A Afanador1, Diana R Tomchick2, Margaret A Phillips3

  • 1Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.

Structure (London, England : 1993)
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Summary

Trypanosoma brucei deoxyhypusine synthase (TbDHS) requires two paralogs for activity, forming a shared active site at their interface. This structure reveals drug targets for treating African sleeping sickness.

Keywords:
Trypanosoma bruceideoxyhypusine synthaseeIF5Ahypusinepolyaminespseudoenzymetrypanosomatids

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Area of Science:

  • Biochemistry
  • Structural Biology
  • Parasitology

Background:

  • Trypanosoma brucei causes African sleeping sickness, a neglected tropical disease.
  • Spermidine is vital for hypusine modification of eukaryotic initiation factor 5A (eIF5A), a process catalyzed by deoxyhypusine synthase (TbDHS).
  • In trypanosomatids, TbDHS activity depends on two paralogs, DHSc and DHSp, which have low individual activity.

Purpose of the Study:

  • To elucidate the structural basis of TbDHS activity.
  • To identify potential drug targets for treating T. brucei infections.

Main Methods:

  • X-ray crystallography of TbDHS.
  • Site-directed mutagenesis and functional analysis.

Main Results:

  • The functional active site of TbDHS is formed at the DHSc/DHSp heterodimer interface, with each subunit complementing the other's catalytic deficiencies.
  • Two NAD+ binding sites exist per heterodimer: a functional catalytic site and a remnant dead site.
  • The dead site influences the catalytic site, suggesting long-range allosteric effects.

Conclusions:

  • The heterodimeric structure of TbDHS is essential for its enzymatic function.
  • Structural differences between T. brucei and human DHS present opportunities for selective drug development against African sleeping sickness.