3I6X

Crystal structure of the calponin homology domain of IQGAP1


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.50 Å
  • R-Value Free: 0.263 
  • R-Value Work: 0.234 

wwPDB Validation   3D Report Full Report


This is version 1.3 of the entry. See complete history


Literature

The IQGAP1 N-terminus Forms Dimers and the Dimer Interface is Required for Binding F-actin and Ca2+/calmodulin.

Liu, J.Kurella, V.B.Lecour, L.Vanagunas, T.Worthylake, D.K.

(2016) Biochemistry 

  • DOI: 10.1021/acs.biochem.6b00745
  • Primary Citation of Related Structures:  
    3I6X, 5L0O

  • PubMed Abstract: 
  • IQGAP1 is a multidomain scaffold protein involved in many cellular processes. We have determined the crystal structure of an N-terminal fragment spanning residues 1-191 (CHDF hereafter) that contains the entire calponin homology domain. The structure of ...

    IQGAP1 is a multidomain scaffold protein involved in many cellular processes. We have determined the crystal structure of an N-terminal fragment spanning residues 1-191 (CHDF hereafter) that contains the entire calponin homology domain. The structure of the CHDF is very similar to those of other type 3 calponin homology domains like those from calponin, Vav, and the yeast IQGAP1 ortholog Rng2. However, in the crystal, two CHDF molecules form a "head-to-head" or parallel dimer through mostly hydrophobic interactions. Binding experiments indicate that the CHDF binds to both F-actin and Ca 2+ /calmodulin, but binding is mutually exclusive. On the basis of the structure, two dimer interface substitutions were introduced. While CHDFL157D disrupts the dimer in gel filtration experiments, oxidized CHDFK161C stabilizes the dimer. These results imply that the CHDF forms the same dimer in solution that is seen in the crystal structure. The disulfide-stabilized dimer displays a reduced level of F-actin binding in sedimentation assays and shows no binding to Ca 2+ /calmodulin in isothermal titration calorimetry (ITC) experiments, indicating that interface residues are utilized for both binding events. The Calmodulin Target Database predicts that residues 93 KK 94 are important for CaM binding, and indeed, the 93 EE 94 double mutation displays a reduced level of binding to Ca 2+ /calmodulin in ITC experiments. Our results indicate that the CHDF dimer interface is used for both F-actin and Ca 2+ /calmodulin binding, and the 93 KK 94 pair, near the interface, is also used for Ca 2+ /calmodulin binding. These results are also consistent with full-length IQGAP1 forming a parallel homodimer.


    Organizational Affiliation

    Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center-New Orleans , 1901 Perdido Street, New Orleans, Louisiana 70112, United States.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Ras GTPase-activating-like protein IQGAP1 ABCD193Homo sapiensMutation(s): 0 
Gene Names: IQGAP1KIAA0051
Find proteins for P46940 (Homo sapiens)
Explore P46940 
Go to UniProtKB:  P46940
NIH Common Fund Data Resources
PHAROS:  P46940
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.50 Å
  • R-Value Free: 0.263 
  • R-Value Work: 0.234 
  • Space Group: P 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 57.432α = 99.55
b = 66.421β = 104.07
c = 83.014γ = 108.69
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling
AMoREphasing
CNSrefinement
PDB_EXTRACTdata extraction
HKL-2000data collection

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

  • Deposited Date: 2009-07-07 
  • Released Date: 2010-07-21 
  • Deposition Author(s): Kurella, V.B.

Revision History 

  • Version 1.0: 2010-07-21
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2016-11-16
    Changes: Database references
  • Version 1.3: 2017-11-01
    Changes: Refinement description