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.