title: Acid unfolding and self-association of recombinant Escherichia coli derived human interferon gamma.
abstract: The secondary and tertiary structure of recombinant human interferon gamma, determined by far- and near-UV circular dichroism, showed a transition from the native state to an unfolded state below pH 4.5. The acid unfolding was extensively studied at pH 3.5 as a function of NaCl concentration. Addition of 0.05-0.2 M NaCl to a pH 3.5 sample increased the amount of beta-sheet structure with no change in the amount of alpha-helix and also induced reversible self-association of interferon gamma to form large aggregates from the monomer. When samples at pH 3.5 were dialyzed against 0.1 M ammonium acetate (pH 6.9) to refold interferon gamma, the samples that contained NaCl in acid formed aggregates upon dialysis while those without NaCl formed a dimer apparently identical with the starting protein (i.e., before acid treatment). Thus, the self-association of interferon gamma in acid is closely correlated with its aggregation behavior in 0.1 M ammonium acetate after removal of acid.
mesh_terms: D002942:Circular Dichroism; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007371:Interferon-gamma; D008970:Molecular Weight; D009994:Osmolar Concentration; D011487:Protein Conformation; D011994:Recombinant Proteins
chemical_list: D011994:Recombinant Proteins; D007371:Interferon-gamma