Effect of α-crystallin on thermal denaturation and aggregation of rabbit muscle glyceraldehyde-3 phosphate dehydrogenase

The study of thermal denaturation of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in the presence of alpha-crystallin by differential scanning calorimetry (DSC) showed that the position of the maximum on the DSC profile (T-max) was shifted toward lower temperatures with increasing alpha-crystallin concentration. The diminishing GAPDH stability in the presence of alpha-crystallin has been explained assuming that beating of GAPDH induces dissociation of the tetrameric form of the enzyme into dimers interacting with alpha-crystallin. The dissociation of the enzyme tetramer was shown by sedimentation velocity at 45 degrees C. Suppression of thermal aggregation of GAPDH by alpha-crystallin was studied by dynamic light scattering under the conditions wherein temperature was elevated at a constant rate. The construction of the light scattering intensity versus the hydrodynamic radius (R-h) plots enabled estimating the hydrodynamic radius of the start aggregates (R-h,R-o)- When aggregation of GAPDH was studied in the presence of alpha-crystallin, the start aggregates of lesser size were observed. (c) 2006 Elsevier B.V. All rights reserved.