α-to-β Structural Transformation of Ovalbumin: Heat and pH Effects
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- Hu, H.Y. & Du, H.N. J Protein Chem (2000) 19: 177. doi:10.1023/A:1007099502179
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Ovalbumin is an important member of the serpin superfamily without inhibitory activity. The heat- and pH-induced α-to-β structural transformations of ovalbumin were investigated by means of circular dichroism and binding of ANS and Congo red dyes. The native ovalbumin shows a mixture of α-helix and β-sheet, while both the heat and alkali treatments are able to transform the native protein into a predominance of β-sheet secondary structure. The free energy changes during transitions to the unfolded state are 5.19 kcal/mol from the native state and 4.00 kcal/mol from the heat-treated one. The binding abilities of the heat-treated and the alkali-treated forms to ANS and Congo red suggest that the altered forms exhibit hydrophobic exposure and intermolecular interaction. The results substantiate that the altered protein forms bearing increased β-sheet structures are prone to aggregation, which is implicated in the pathogenesis of some conformational diseases.