Comparative Fourier transform infrared spectroscopy study of cold-, pressure-, and heat-induced unfolding and aggregation of myoglobin.
We studied the cold unfolding of myoglobin with Fourier transform infrared spectroscopy and compared it with pressure and heat unfolding. Because protein aggregation is a phenomenon with medical as well as biotechnological implications, we were interested in both the structural changes as well as the aggregation behavior of the respective unfolded states. The cold- and pressure-induced unfolding both yield a partially unfolded state characterized by a persistent amount of secondary structure, in which a stable core of G and H helices is preserved. In this respect the cold- and pressure-unfolded states show a resemblance with an early folding intermediate of myoglobin. In contrast, the heat unfolding results in the formation of the infrared bands typical of intermolecular antiparallel beta-sheet aggregation. This implies a transformation of alpha-helix into intermolecular beta-sheet. H/2H-exchange data suggest that the helices are first unfolded and then form intermolecular beta-sheets. The pressure and cold unfolded states do not give rise to the intermolecular aggregation bands that are typical for the infrared spectra of many heat-unfolded proteins. This suggests that the pathways of the cold and pressure unfolding are substantially different from that of the heat unfolding. After return to ambient conditions the cold- or pressure-treated proteins adopt a partially refolded conformation. This aggregates at a lower temperature (32 degrees C) than the native state (74 degrees C).
Meersman
Filip
F
Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium.
Smeller
László
L
Heremans
Karel
K
D000818:Animals; D003080:Cold Temperature; D006736:Horses; D006358:Hot Temperature; D008958:Models, Molecular; D009206:Myocardium / Q000737:chemistry; D009211:Myoglobin / Q000737:chemistry*; D011312:Pressure; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D021122:Protein Subunits; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
D009211:Myoglobin; D021122:Protein Subunits