Crystal structure of human STAT1 in complex with the repeat region from Toxoplasma protein TgIST

Experimental Data Snapshot

  • Resolution: 2.97 Å
  • R-Value Free: 0.288 
  • R-Value Work: 0.248 
  • R-Value Observed: 0.250 

wwPDB Validation   3D Report Full Report

This is version 1.2 of the entry. See complete history


The intrinsically disordered protein TgIST from Toxoplasma gondii inhibits STAT1 signaling by blocking cofactor recruitment.

Huang, Z.Liu, H.Nix, J.Xu, R.Knoverek, C.R.Bowman, G.R.Amarasinghe, G.K.Sibley, L.D.

(2022) Nat Commun 13: 4047-4047

  • DOI: https://doi.org/10.1038/s41467-022-31720-7
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Signal transducer and activator of transcription (STAT) proteins communicate from cell-surface receptors to drive transcription of immune response genes. The parasite Toxoplasma gondii blocks STAT1-mediated gene expression by secreting the intrinsically disordered protein TgIST that traffics to the host nucleus, binds phosphorylated STAT1 dimers, and occupies nascent transcription sites that unexpectedly remain silenced. Here we define a core region within internal repeats of TgIST that is necessary and sufficient to block STAT1-mediated gene expression. Cellular, biochemical, mutational, and structural data demonstrate that the repeat region of TgIST adopts a helical conformation upon binding to STAT1 dimers. The binding interface is defined by a groove formed from two loops in the STAT1 SH2 domains that reorient during dimerization. TgIST binding to this newly exposed site at the STAT1 dimer interface alters its conformation and prevents the recruitment of co-transcriptional activators, thus defining the mechanism of blocked transcription.

  • Organizational Affiliation

    Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, 63110, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Signal transducer and activator of transcription 1-alpha/beta,Inhibitor of STAT1-dependent transcription TgIST642Homo sapiensToxoplasma gondii GT1
This entity is chimeric
Mutation(s): 0 
Gene Names: STAT1TGRH88_087790
UniProt & NIH Common Fund Data Resources
Find proteins for P42224 (Homo sapiens)
Explore P42224 
Go to UniProtKB:  P42224
PHAROS:  P42224
GTEx:  ENSG00000115415 
Find proteins for A0A7J6KA90 (Toxoplasma gondii)
Explore A0A7J6KA90 
Go to UniProtKB:  A0A7J6KA90
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupsP42224A0A7J6KA90
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.97 Å
  • R-Value Free: 0.288 
  • R-Value Work: 0.248 
  • R-Value Observed: 0.250 
  • Space Group: C 2 2 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 59.96α = 90
b = 163.92β = 90
c = 226.86γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
Aimlessdata scaling

Structure Validation

View Full Validation Report

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)United StatesAI118426

Revision History  (Full details and data files)

  • Version 1.0: 2022-07-06
    Type: Initial release
  • Version 1.1: 2023-01-18
    Changes: Database references
  • Version 1.2: 2023-10-25
    Changes: Data collection, Refinement description