A mechanical unfolding intermediate in an actin-crosslinking protein

Nat Struct Mol Biol. 2004 Jan;11(1):81-5. doi: 10.1038/nsmb705. Epub 2003 Dec 29.


Many F-actin crosslinking proteins consist of two actin-binding domains separated by a rod domain that can vary considerably in length and structure. In this study, we used single-molecule force spectroscopy to investigate the mechanics of the immunoglobulin (Ig) rod domains of filamin from Dictyostelium discoideum (ddFLN). We find that one of the six Ig domains unfolds at lower forces than do those of all other domains and exhibits a stable unfolding intermediate on its mechanical unfolding pathway. Amino acid inserts into various loops of this domain lead to contour length changes in the single-molecule unfolding pattern. These changes allowed us to map the stable core of approximately 60 amino acids that constitutes the unfolding intermediate. Fast refolding in combination with low unfolding forces suggest a potential in vivo role for this domain as a mechanically extensible element within the ddFLN rod.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Animals
  • Contractile Proteins / chemistry*
  • Contractile Proteins / genetics
  • Contractile Proteins / metabolism
  • Cross-Linking Reagents
  • Dictyostelium / genetics
  • Dictyostelium / metabolism
  • Dimerization
  • Filamins
  • In Vitro Techniques
  • Microfilament Proteins / chemistry*
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism
  • Microscopy, Atomic Force
  • Mutagenesis, Site-Directed
  • Protein Denaturation
  • Protein Folding
  • Protein Structure, Tertiary
  • Protozoan Proteins / chemistry*
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism


  • Actins
  • Contractile Proteins
  • Cross-Linking Reagents
  • Filamins
  • Microfilament Proteins
  • Protozoan Proteins