Amyloid-like fibril formation in an all beta-barrel protein involves the formation of partially structured intermediate(s)

J Biol Chem. 2002 May 24;277(21):19027-36. doi: 10.1074/jbc.M110762200. Epub 2002 Mar 4.

Abstract

In the present study, we demonstrate the thermal induced amyloid formation in a beta-barrel protein, such as the acidic fibroblast growth factor from Notopthalmus viridescens (nFGF-1). Fibril formation in nFGF-1 is observed to occur maximally at 65 degrees C. Electron microscope analysis of the thermal induced fibrils of nFGF-1 shows that they are filamentous with an average diameter of about 20 nm. X-ray diffraction analysis reveals that the thermal induced fibrils of nFGF-1 have a typical "cross-beta" structure with the beta-strands perpendicular to the fibril axis. By using a variety of biophysical techniques including multidimensional NMR, we demonstrate that fibril formation involves the formation of a partially structured intermediate(s) in the thermal unfolding pathway of the protein (nFGF-1). Results of the anilino-8-napthalene sulfonate binding experiments indicate that fibril formation occurs due to the coalescence of the protein (in the intermediate state(s)) through the solvent-exposed non-polar surface(s). In this study, we also demonstrate that organic osmolytes, such as proline, can efficiently prevent the thermal induced amyloid formation in nFGF-1. Proline is found to stabilize the native conformation of the protein. The addition, proline is observed to increase the cooperativity of the unfolding (native <--> denatured) reaction and consequently decrease the population of the "sticky" thermal equilibrium intermediate(s) responsible for the fibril formation.

MeSH terms

  • Amyloid / biosynthesis*
  • Amyloid / chemistry
  • Amyloid / ultrastructure
  • Animals
  • Circular Dichroism
  • Fibroblast Growth Factor 1 / chemistry
  • Fibroblast Growth Factor 1 / metabolism*
  • Hot Temperature
  • Microscopy, Electron
  • Models, Molecular
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Conformation
  • Protein Denaturation
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Salamandridae
  • Spectroscopy, Fourier Transform Infrared
  • X-Ray Diffraction

Substances

  • Amyloid
  • Recombinant Proteins
  • Fibroblast Growth Factor 1