Heat-induced changes in the conformation of α- and β-crystalline: Unique thermal stability of α-crystallin

Abstract Of the crystallin proteins of the lens, the principal subunit of the β-crystallin, βB2 (βBp), has been considered to be the only heat-stable protein because it does not precipitate upon heating. In our recent investigations, however, we have found that the α-crystallin from bovine lenses is not only heat stable but also does not denature at temperatures up to 100°C. Using circular dichroism and fluorescence to monitor the conformational changes of α- and βB2-crystallins upon heating, we found that α-crystallin maintains a high degree of structure, whereas the βB2-crystallin shows a reversible sigmoidal order-disorder transition at about 58°C.