Purification and SAXS analysis of the integrin linked kinase, PINCH, parvin (IPP) heterotrimeric complex

PLoS One. 2013;8(1):e55591. doi: 10.1371/journal.pone.0055591. Epub 2013 Jan 31.

Abstract

The heterotrimeric protein complex containing the integrin linked kinase (ILK), parvin, and PINCH proteins, termed the IPP complex, is an essential component of focal adhesions, where it interacts with many proteins to mediate signaling from integrin adhesion receptors. Here we conduct a biochemical and structural analysis of the minimal IPP complex, comprising full-length human ILK, the LIM1 domain of PINCH1, and the CH2 domain of α-parvin. We provide a detailed purification protocol for IPP and show that the purified IPP complex is stable and monodisperse in solution. Using small-angle X-ray scattering (SAXS), we also conduct the first structural characterization of IPP, which reveals an elongated shape with dimensions 120×60×40 Å. Flexibility analysis using the ensemble optimization method (EOM) is consistent with an IPP complex structure with limited flexibility, raising the possibility that inter-domain interactions exist. However, our studies suggest that the inter-domain linker in ILK is accessible and we detect no inter-domain contacts by gel filtration analysis. This study provides a structural foundation to understand the conformational restraints that govern the IPP complex.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adaptor Proteins, Signal Transducing / chemistry*
  • Adaptor Proteins, Signal Transducing / genetics
  • Cytoskeletal Proteins / chemistry*
  • Cytoskeletal Proteins / genetics
  • Humans
  • LIM Domain Proteins / chemistry*
  • LIM Domain Proteins / genetics
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Models, Molecular
  • Multiprotein Complexes / chemistry*
  • Multiprotein Complexes / isolation & purification
  • Protein Binding
  • Protein Conformation
  • Protein Interaction Domains and Motifs
  • Protein Serine-Threonine Kinases / chemistry*
  • Protein Serine-Threonine Kinases / genetics
  • Scattering, Small Angle*
  • X-Ray Diffraction*

Substances

  • Adaptor Proteins, Signal Transducing
  • Cytoskeletal Proteins
  • IPP protein, human
  • LIM Domain Proteins
  • LIMS1 protein, human
  • Membrane Proteins
  • Multiprotein Complexes
  • integrin-linked kinase
  • Protein Serine-Threonine Kinases