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 exclusio n chromatography. The thermal transition of alpha-crystallin proceeds at T-trs = 59.8 +/- 0.6 degrees C with an enthalpy change of Delta H = 336 +/- 9 kJ per mol subunit, Disagreement between previous Delta H v alues 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-cry stallin is the monomeric subunit.