3WSA

The Tuberculosis Drug SQ109 Inhibits Trypanosoma cruzi Cell Proliferation and acts Synergistically with Posaconazole


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.90 Å
  • R-Value Free: 0.261 
  • R-Value Work: 0.206 

Starting Model: experimental
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Literature

SQ109, a new drug lead for Chagas disease.

Veiga-Santos, P.Li, K.Lameira, L.de Carvalho, T.M.Huang, G.Galizzi, M.Shang, N.Li, Q.Gonzalez-Pacanowska, D.Hernandez-Rodriguez, V.Benaim, G.Guo, R.T.Urbina, J.A.Docampo, R.de Souza, W.Oldfield, E.

(2015) Antimicrob Agents Chemother 59: 1950-1961

  • DOI: https://doi.org/10.1128/AAC.03972-14
  • Primary Citation of Related Structures:  
    3WSA

  • PubMed Abstract: 

    We tested the antituberculosis drug SQ109, which is currently in advanced clinical trials for the treatment of drug-susceptible and drug-resistant tuberculosis, for its in vitro activity against the trypanosomatid parasite Trypanosoma cruzi, the causative agent of Chagas disease. SQ109 was found to be a potent inhibitor of the trypomastigote form of the parasite, with a 50% inhibitory concentration (IC50) for cell killing of 50 ± 8 nM, but it had little effect (50% effective concentration [EC50], ∼80 μM) in a red blood cell hemolysis assay. It also inhibited extracellular epimastigotes (IC50, 4.6 ± 1 μM) and the clinically relevant intracellular amastigotes (IC50, ∼0.5 to 1 μM), with a selectivity index of ∼10 to 20. SQ109 caused major ultrastructural changes in all three life cycle forms, as observed by light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It rapidly collapsed the inner mitochondrial membrane potential (Δψm) in succinate-energized mitochondria, acting in the same manner as the uncoupler FCCP [carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone], and it caused the alkalinization of internal acidic compartments, effects that are likely to make major contributions to its mechanism of action. The compound also had activity against squalene synthase, binding to its active site; it inhibited sterol side-chain reduction and, in the amastigote assay, acted synergistically with the antifungal drug posaconazole, with a fractional inhibitory concentration index (FICI) of 0.48, but these effects are unlikely to account for the rapid effects seen on cell morphology and cell killing. SQ109 thus most likely acts, at least in part, by collapsing Δψ/ΔpH, one of the major mechanisms demonstrated previously for its action against Mycobacterium tuberculosis. Overall, the results suggest that SQ109, which is currently in advanced clinical trials for the treatment of drug-susceptible and drug-resistant tuberculosis, may also have potential as a drug lead against Chagas disease.


  • Organizational Affiliation

    Laboratório de Ultraestrutura Celular Hertha Meyer, CCS, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Bloco G, Ilha do Fundão, Rio de Janeiro, Brazil Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Squalene synthase
A, B, C, D, E
A, B, C, D, E, F
360Homo sapiensMutation(s): 3 
Gene Names: FDFT1
EC: 2.5.1.21
UniProt & NIH Common Fund Data Resources
Find proteins for P37268 (Homo sapiens)
Explore P37268 
Go to UniProtKB:  P37268
PHAROS:  P37268
GTEx:  ENSG00000079459 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP37268
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.90 Å
  • R-Value Free: 0.261 
  • R-Value Work: 0.206 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 85.75α = 90
b = 154.006β = 91.38
c = 90.615γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
PHASERphasing
CNSrefinement
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Ligand Structure Quality Assessment 


Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2015-04-01
    Type: Initial release
  • Version 1.1: 2023-11-08
    Changes: Data collection, Database references, Derived calculations, Refinement description
  • Version 1.2: 2024-03-13
    Changes: Database references