Identification of first-in-class plasmodium OTU inhibitors with potent anti-malarial activity

Biochem J. 2021 Sep 30;478(18):3445-3466. doi: 10.1042/BCJ20210481.


OTU proteases antagonize the cellular defense in the host cells and involve in pathogenesis. Intriguingly, P. falciparum, P. vivax, and P. yoelii have an uncharacterized and highly conserved viral OTU-like proteins. However, their structure, function or inhibitors have not been previously reported. To this end, we have performed structural modeling, small molecule screening, deconjugation assays to characterize and develop first-in-class inhibitors of P. falciparum, P. vivax, and P. yoelii OTU-like proteins. These Plasmodium OTU-like proteins have highly conserved residues in the catalytic and inhibition pockets similar to viral OTU proteins. Plasmodium OTU proteins demonstrated Ubiquitin and ISG15 deconjugation activities as evident by intracellular ubiquitinated protein content analyzed by western blot and flow cytometry. We screened a library of small molecules to determine plasmodium OTU inhibitors with potent anti-malarial activity. Enrichment and correlation studies identified structurally similar molecules. We have identified two small molecules that inhibit P. falciparum, P. vivax, and P. yoelii OTU proteins (IC50 values as low as 30 nM) with potent anti-malarial activity (IC50 of 4.1-6.5 µM). We also established enzyme kinetics, druglikeness, ADME, and QSAR model. MD simulations allowed us to resolve how inhibitors interacted with plasmodium OTU proteins. These findings suggest that targeting malarial OTU-like proteases is a plausible strategy to develop new anti-malarial therapies.

Keywords: Plasmodium; OTU-like dubs; anti-malarial; intracellular parasite.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antimalarials / chemistry
  • Antimalarials / pharmacology*
  • Binding Sites
  • Erythrocytes / drug effects
  • Erythrocytes / parasitology
  • Gene Expression
  • High-Throughput Screening Assays
  • Humans
  • Inhibitory Concentration 50
  • Molecular Docking Simulation
  • Molecular Dynamics Simulation
  • Peptide Hydrolases / chemistry*
  • Peptide Hydrolases / genetics
  • Peptide Hydrolases / metabolism
  • Plasmodium falciparum / drug effects*
  • Plasmodium falciparum / enzymology
  • Plasmodium falciparum / genetics
  • Plasmodium falciparum / growth & development
  • Plasmodium vivax / drug effects*
  • Plasmodium vivax / enzymology
  • Plasmodium vivax / genetics
  • Plasmodium vivax / growth & development
  • Plasmodium yoelii / drug effects*
  • Plasmodium yoelii / enzymology
  • Plasmodium yoelii / genetics
  • Plasmodium yoelii / growth & development
  • Protease Inhibitors / chemistry
  • Protease Inhibitors / pharmacology*
  • Protein Binding
  • Protein Conformation
  • Protein Interaction Domains and Motifs
  • Protozoan Proteins / antagonists & inhibitors
  • Protozoan Proteins / chemistry*
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism
  • Quantitative Structure-Activity Relationship
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Small Molecule Libraries / chemistry
  • Small Molecule Libraries / pharmacology
  • Ubiquitin / genetics
  • Ubiquitin / metabolism
  • Ubiquitination


  • Antimalarials
  • Protease Inhibitors
  • Protozoan Proteins
  • Recombinant Proteins
  • Small Molecule Libraries
  • Ubiquitin
  • Peptide Hydrolases