A bacteriophage capsid protein provides a general amyloid interaction motif (GAIM) that binds and remodels misfolded protein assemblies

J Mol Biol. 2014 Jun 26;426(13):2500-19. doi: 10.1016/j.jmb.2014.04.015. Epub 2014 Apr 22.


Misfolded protein aggregates, characterized by a canonical amyloid fold, play a central role in the pathobiology of neurodegenerative diseases. Agents that bind and sequester neurotoxic intermediates of amyloid assembly, inhibit the assembly or promote the destabilization of such protein aggregates are in clinical testing. Here, we show that the gene 3 protein (g3p) of filamentous bacteriophage mediates potent generic binding to the amyloid fold. We have characterized the amyloid binding and conformational remodeling activities using an array of techniques, including X-ray fiber diffraction and NMR. The mechanism for g3p binding with amyloid appears to reflect its physiological role during infection of Escherichia coli, which is dependent on temperature-sensitive interdomain unfolding and cis-trans prolyl isomerization of g3p. In addition, a natural receptor for g3p, TolA-C, competitively interferes with Aβ binding to g3p. NMR studies show that g3p binding to Aβ fibers is predominantly through middle and C-terminal residues of the Aβ subunit, indicating β strand-g3p interactions. A recombinant bivalent g3p molecule, an immunoglobulin Fc (Ig) fusion of the two N-terminal g3p domains, (1) potently binds Aβ fibers (fAβ) (KD=9.4nM); (2); blocks fAβ assembly (IC50~50nM) and (3) dissociates fAβ (EC50=40-100nM). The binding of g3p to misfolded protein assemblies is generic, and amyloid-targeted activities can be demonstrated using other misfolded protein systems. Taken together, our studies show that g3p(N1N2) acts as a general amyloid interaction motif.

Keywords: Ig fusion; amyloid; amyloid remodeling; gene 3 protein.

MeSH terms

  • Amyloid beta-Peptides / chemistry*
  • Amyloid beta-Peptides / metabolism*
  • Bacterial Outer Membrane Proteins / chemistry
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacteriophage M13 / genetics
  • Bacteriophage M13 / metabolism*
  • Capsid Proteins / chemistry*
  • Capsid Proteins / genetics
  • Capsid Proteins / metabolism*
  • Escherichia coli Proteins / chemistry
  • Escherichia coli Proteins / metabolism
  • Humans
  • Kinetics
  • Membrane Transport Proteins / chemistry
  • Membrane Transport Proteins / metabolism
  • Models, Molecular
  • Neurodegenerative Diseases / etiology
  • Neurodegenerative Diseases / metabolism
  • Protein Binding
  • Protein Conformation
  • Protein Folding
  • Protein Interaction Domains and Motifs
  • Protein Multimerization
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • alpha-Synuclein / chemistry
  • alpha-Synuclein / metabolism
  • tau Proteins / chemistry
  • tau Proteins / metabolism


  • Amyloid beta-Peptides
  • Bacterial Outer Membrane Proteins
  • Capsid Proteins
  • Escherichia coli Proteins
  • MAPT protein, human
  • Membrane Transport Proteins
  • Recombinant Fusion Proteins
  • alpha-Synuclein
  • tau Proteins
  • tolA protein, E coli
  • tolC protein, E coli