Refolding of a high molecular weight protein: salt effect on collapse.
Small-angle neutron scattering experiments were performed on dilute solutions of a high molecular weight protein (fibronectin, M = 580 kg/mol) in four cases: native conditions; unfolded state obtained by a denaturing agent (urea); and two badly refolded (or collapsed) states obtained by progressive elimination of the denaturing agent in salt-containing or salt-free solutions. Our main result is concerned by the conformation of the protein as the attempt for refolding is driven with or without salt. In salt-containing solution, we observe unambiguously that the protein chain collapses at large length scales but still obeys to a Gaussian statistics at short length scales. In other words, the globule embodies a large quantity of solvent compared to the compact situation. In salt-free solutions, the badly refolded protein is not globular but displays both a coil-like and an open conformation at large length scales and a local high density area. This behavior is discussed with respect to the scaling theories for polymers and polyampholytes.
Lairez
D
D
Laboratoire Léon Brillouin, Gif-sur-Yvette, France.
Pauthe
E
E
Pelta
J
J
D003198:Computer Simulation; D005353:Fibronectins / Q000737:chemistry*; D006801:Humans; D046911:Macromolecular Substances; D008958:Models, Molecular; D015233:Models, Statistical; D008970:Molecular Weight; D033363:Neutron Diffraction / Q000379:methods*; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D012492:Salts / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry*; D012996:Solutions; D014508:Urea / Q000737:chemistry*
D005353:Fibronectins; D046911:Macromolecular Substances; D012492:Salts; D012996:Solutions; D012965:Sodium Chloride; D014508:Urea