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The thermal unfolding and reversibility of temperature-induced changes in alpha(sub 1)-acid glycoprotein (AGP) is investigated in FT-IR spectroscopy. The resemblance of AGP and odorant-binding protein (OBP) 3D structures confirmed the similarities of data obtained using FT-IR spectroscopy.

Results show that sodium cation induces GTPase activity and the anions modulate the enzyme activity through destabilization of regions of elongation factor 1-alpha from Sulfolobus solfataricus. Infrared analysis indicate particular regions of the polypeptide undergoing structural confromational changes.

Despite extensive investigations on thermal denaturation of alpha(1)-acid glycoprotein (AGP) using a variety of techniques, structural features of the folded-unfolded state in terms of residual secondary structures and the structural transitions involved in this process have not been fully characterized. In this study we employed FT-IR spectroscopy to investigate the thermal unfolding and reversibility of temperature-induced changes in AGP. The data revealed a fully reversible beta-sheet-rich protein which exhibits a molten globule-like state, an important protein folding intermediate. 2D-IR COS revealed the sequence of the conformational changes occurring before denaturation and confirmed the formation of this intermediate which was further supported by CD spectroscopy. On account of the similarities in the FT-IR spectra of AGP with those of porcine odorant-binding protein (OBP), homology modeling of AGP using OBP as template was performed. The resemblance of AGP and OBP 3D structures confirmed the similarities of data obtained using FT-IR spectroscopy. Overall, FT-IR spectroscopy appears to be useful for investigating the structural characteristics and stability of proteins whose 3D structures are unavailable and for assessing the molten globule-like state in small beta-sheet-rich proteins.