title: The repeating segments of the F-actin cross-linking gelation factor (ABP-120) have an immunoglobulin-like fold.
abstract: 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.
authors.affiliation: Max Planck Institute for Biochemistry, Martinsried, F.R.G.
authors.forename: P
authors.initials: P
authors.lastname: Fucini
authors.forename: C
authors.initials: C
authors.lastname: Renner
authors.forename: C
authors.initials: C
authors.lastname: Herberhold
authors.forename: A A
authors.initials: AA
authors.lastname: Noegel
authors.forename: T A
authors.initials: TA
authors.lastname: Holak
mesh_terms: D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D003198:Computer Simulation; D004023:Dictyostelium / Q000378:metabolism; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008840:Microfilament Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity
chemical_list: D000199:Actins; D002352:Carrier Proteins; D007136:Immunoglobulins; D008840:Microfilament Proteins; D011994:Recombinant Proteins; C060680:abpC protein, Dictyostelium