On the thermal stability of alpha-crystallin: a new insight from infrared spectroscopy.
alpha-Crystallin is a major structural protein of the vertebrate lens which shows structural and functional similarities to small heat shock proteins. The structure and the thermal stability of bovine alpha-crystallin were studied by Fourier-transform infrared spectroscopy, circular dichroism, and differential scanning calorimetry. Infrared spectroscopic data provide evidence which corroborates the view that the secondary structure of alpha-crystallin is highly ordered and consists predominantly of beta-sheets. However, the present results fail to support the widespread notion of an extremely high thermal stability of the protein. All three experimental approaches used in this study show that alpha-crystallin undergoes a major thermotropic transition with a midpoint at 60-62 degrees C. Furthermore, Fourier-transform infrared spectra provide evidence that this conformational transition is associated with a massive loss of the native beta-sheet structure. These results shed new light on structural properties of alpha-crystallin and have important implications for understanding the mechanism of the chaperone-like action of this protein.
Surewicz
W K
WK
Mason Institute of Ophthalmology, University of Missouri, Columbia 65212, USA.
Olesen
P R
PR
D000818:Animals; D002152:Calorimetry, Differential Scanning; D002417:Cattle; D002942:Circular Dichroism; D003459:Crystallins / Q000737:chemistry*; D004355:Drug Stability; D006358:Hot Temperature; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared
D003459:Crystallins