The repeating segments of the F-actin cross-linking gelation factor (ABP-120) have an immunoglobulin-like fold

Nat Struct Biol. 1997 Mar;4(3):223-30. doi: 10.1038/nsb0397-223.


The 120,000 M(r) gelation factor and alpha-actinin are among the most abundant F-actin cross-linking proteins in Dictyostelium discoideum. Both molecules are rod-shaped homodimers. Each monomer chain is comprised of an actin-binding domain and a rod domain. The rod domain of the gelation factor consists of six 100-residue repetitive segments with high internal homology. We have now determined the three-dimensional structure of segment 4 of the rod domain of the gelation factor from D. discoideum using NMR spectroscopy. The segment consists of seven beta-sheets arranged in an immunoglobulin-like (Ig) fold. This is completely different from the alpha-actinin rod domain which consists of four spectrin-like alpha-helical segments. The gelation factor is the first example of an Ig-fold found in an actin-binding protein. Two highly homologous actin-binding proteins from human with similar sequences to the gelation factor, filamin and a 280,000 M(r) actin-binding protein (ABP-280), share conserved residues that form the core of the gelation factor repetitive segment structure. Thus, the segment 4 structure should be common to this subfamily of the spectrin superfamily. The structure of segment 4 together with previously published electron microscopy data, provide an explanation for the dimerization of the whole gelation factor molecule.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Amino Acid Sequence
  • Animals
  • Carrier Proteins / chemistry*
  • Carrier Proteins / metabolism
  • Computer Simulation
  • Dictyostelium / metabolism
  • Humans
  • Immunoglobulins / chemistry*
  • Magnetic Resonance Spectroscopy / methods
  • Microfilament Proteins / chemistry*
  • Microfilament Proteins / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Folding*
  • Protein Structure, Secondary*
  • Recombinant Proteins / chemistry
  • Sequence Homology, Amino Acid
  • Static Electricity


  • Actins
  • Carrier Proteins
  • Immunoglobulins
  • Microfilament Proteins
  • Recombinant Proteins
  • abpC protein, Dictyostelium