The conformational stability of alpha-crystallin is rather low: calorimetric results

The eye lens protein and chaperonin, alpha-crystallin, was studied by differential scanning microcalorimetry, spectroscopy and size exclusion chromatography. The thermal transition of alpha-crystallin proceeds at Ttrs = 59.8 +/- 0.6 degrees C with an enthalpy change of delta H = 336 +/- 9 kJ per mol subunit. Disagreement between previous delta H values could be attributed to a side reaction that leads, depending on the scan rate, to the formation of a non-productive folding form. The conformational stability of alpha-crystallin is rather low (delta G = 24 +/- 5 kJ/mol of subunit). The minimal cooperative unit of alpha-crystallin is the monomeric subunit.