Biological Assembly 1  

 3D View: Structure | Electron Density

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 1 assigned by authors and generated by PISA (software)

Macromolecule Content

• Total Structure Weight: 18.33 kDa 
• Atom Count: 998 
• Residue Count: 124 
• Unique protein chains: 1

4CHJ

Structure of Inner Membrane Complex (IMC) Sub-compartment Protein 3 (ISP3) from Toxoplasma gondii

• DOI: 10.2210/pdb4CHJ/pdb

• Classification: CELL CYCLE
• Organism(s): Toxoplasma gondii ME49
• Expression System: Escherichia coli BL21(DE3)
• Mutation(s): No 


• Deposited: 2013-12-03 Released: 2014-04-09 
• Deposition Author(s): Tonkin, M.L., Beck, J.R., Bradley, P.J., Boulanger, M.J.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2.32 Å
• R-Value Free: 0.268 
• R-Value Work: 0.218 
• R-Value Observed: 0.221 

Literature

The Inner Membrane Complex Sub-Compartment Proteins Critical for Replication of the Apicomplexan Parasite Toxoplasma Gondii Adopt a Pleckstrin Homology Fold

Tonkin, M.L., Beck, J.R., Bradley, P.J., Boulanger, M.J.

(2014) J Biol Chem 289: 13962

• PubMed: 24675080 
• DOI: 10.1074/jbc.M114.548891
• Primary Citation of Related Structures:  
  4CHJ, 4CHM


• PubMed Abstract: 
  

Toxoplasma gondii, an apicomplexan parasite prevalent in developed nations, infects up to one-third of the human population. The success of this parasite depends on several unique structures including an inner membrane complex (IMC) that lines the interior of the plasma membrane and contains proteins important for gliding motility and replication. Of these proteins, the IMC sub-compartment proteins (ISPs) have recently been shown to play a role in asexual T. gondii daughter cell formation, yet the mechanism is unknown. Complicating mechanistic characterization of the ISPs is a lack of sequence identity with proteins of known structure or function. In support of elucidating the function of ISPs, we first determined the crystal structures of representative members TgISP1 and TgISP3 to a resolution of 2.10 and 2.32 Å, respectively. Structural analysis revealed that both ISPs adopt a pleckstrin homology fold often associated with phospholipid binding or protein-protein interactions. Substitution of basic for hydrophobic residues in the region that overlays with phospholipid binding in related pleckstrin homology domains, however, suggests that ISPs do not retain phospholipid binding activity. Consistent with this observation, biochemical assays revealed no phospholipid binding activity. Interestingly, mapping of conserved surface residues combined with crystal packing analysis indicates that TgISPs have functionally repurposed the phospholipid-binding site likely to coordinate protein partners. Recruitment of larger protein complexes may also be aided through avidity-enhanced interactions resulting from multimerization of the ISPs. Overall, we propose a model where TgISPs recruit protein partners to the IMC to ensure correct progression of daughter cell formation.

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Organizational Affiliation: 

From the Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8W 3P6, Canada and [e-mail].

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
IMC SUB-COMPARTMENT PROTEIN ISP3	A	164	Toxoplasma gondii ME49	Mutation(s): 0
Find proteins for B9PJE6 (Toxoplasma gondii (strain ATCC 50861 / VEG)) Explore B9PJE6  Go to UniProtKB:  B9PJE6

Small Molecules

Modified Residues  1 Unique
ID	Chains	Type	Formula	2D Diagram	Parent
CSX	A	L-PEPTIDE LINKING	C3 H7 N O3 S		CYS

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.32 Å
• R-Value Free: 0.268 
• R-Value Work: 0.218 
• R-Value Observed: 0.221 
• Space Group: I 4₁ 2 2

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 99.48	α = 90
b = 99.48	β = 90
c = 60.87	γ = 90

Software Package:

Software Name	Purpose
REFMAC	refinement
iMOSFLM	data reduction
SCALA	data scaling
PHASER	phasing

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2013-12-03 
• Released Date: 2014-04-09 
Deposition Author(s): Tonkin, M.L., Beck, J.R., Bradley, P.J., Boulanger, M.J.

Revision History 

• Version 1.0: 2014-04-09
  Type: Initial release
  
• Version 1.1: 2014-08-27
  Changes: Database references