Pressure- and temperature-induced unfolding and aggregation of recombinant human interferon-γ: A fourier transform infrared spectroscopy study

Abstract

The effect of hydrostatic pressure on the secondary structure of recombinant human interferon-γ (rhIFN-γ) and its biologically inactive truncated form rhIFN-ΔC15 has been studied using Fourier-transform IR (FTIR) spectroscopy. In situ observation of the pressure-induced changes using the diamond anvil cell shows that the α-helical structure is mainly transformed into disordered structure at high pressure. Increasing pressure also induces the formation of a gel. Addition of 0.5 M MgCl2 significantly reduces the pressure stability. Releasing the pressure below 300 MPa results in the formation of intermolecular antiparallel β-sheets, which is seldom observed. This suggests that the intermolecular β-sheet of rhIFN-γ is stabilized by electrostatic interactions that are disrupted at high pressure. For comparison we also studied the effect of temperature. Temperature-induced changes reflect extensive transformation of α-helical structure into intermolecular antiparallel β-sheet, as is usually observed for most proteins.